Beginners Digest, Vol 47, Issue 25
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Category question (Brent Yorgey) 2. Re: Category question (Manfred Lotz) 3. Re: problems with wxHaskell installation (Miguel Negrao) 4. Re: Category question (Jay Sulzberger) 5. Re: problems with wxHaskell installation (Heinrich Apfelmus) 6. How to solve this using State Monad? (kak dod) -- Message: 1 Date: Mon, 28 May 2012 12:43:33 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Category question To: beginners@haskell.org Message-ID: 20120528164333.ga5...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Mon, May 28, 2012 at 04:14:40PM +0200, Manfred Lotz wrote: For me id: A - A could be defined by: A morphism id: A - A is called identity morphism iff for all x of A we have id(x) = x. This is not actually a valid definition; the notation id(x) = x does not make sense. It seems you are assuming that morphisms represent some sort of function, but that is only true in certain special categories. My point is that in the books about category theory those two statements are stated as axioms, and id is (in many books) just self understood or defined as I have defined it above. If in a book about category the author would say that for each object A there must exist a morphism id: A - A (called identity morphism) which is defined by idB . f = f and f . idA = f then this would be clearer (and better, IMHO). This is exactly what category theory books do (or should) say. Do you have a particular example of a book which does not state things in this way? Note that there is no particular difference between calling these equations axioms or a definition. That is, there is an 'identity morphism' satisfying the following axioms... and there is an 'identity morphism' defined by... are just two different ways of saying the exact same thing. -Brent -- Message: 2 Date: Mon, 28 May 2012 18:50:34 +0200 From: Manfred Lotz manfred.l...@arcor.de Subject: Re: [Haskell-beginners] Category question To: beginners@haskell.org Message-ID: 20120528185034.51ed2...@arcor.com Content-Type: text/plain; charset=US-ASCII On Mon, 28 May 2012 10:57:11 -0400 Brent Yorgey byor...@seas.upenn.edu wrote: On Mon, May 28, 2012 at 04:14:40PM +0200, Manfred Lotz wrote: For me id: A - A could be defined by: A morphism id: A - A is called identity morphism iff for all x of A we have id(x) = x. This is not actually a valid definition; the notation id(x) = x does not make sense. It seems you are assuming that morphisms represent some sort of function, but that is only true in certain special categories. Ok, it is a valid definition only in a certain context. In the far wider context of category theory this indeed makes no sense. My point is that in the books about category theory those two statements are stated as axioms, and id is (in many books) just self understood or defined as I have defined it above. If in a book about category the author would say that for each object A there must exist a morphism id: A - A (called identity morphism) which is defined by idB . f = f and f . idA = f then this would be clearer (and better, IMHO). This is exactly what category theory books do (or should) say. Do you have a particular example of a book which does not state things in this way? In 'Conceptual Mathematics' by F. William Lawvere, Stephen H. Schanuel they define an identity map with fa = a for each a in A. Then on page 17 they define category and say ... Identity Maps: (one per object) 1A: A - A ... Rules for a category 1. The identity laws: where they say g . 1A = g and 1B . f = f 2. associatlve laws ... It seems that this definition of a category is not as general as it could be. Here 1. is something which follows easily from the definition of an identity map. I guess that this made me think of idA as idA(x) = x for each x of A. Later when I saw other (more general) definitions I did not read carefully to realize the difference. Thanks a lot for making this clear to me. -- Manfred -- Message: 3 Date: Mon, 28 May 2012 18:31:08 +0100 From: Miguel Negrao miguel.negrao-li...@friendlyvirus.org Subject: Re: [Haskell-beginners] problems with wxHaskell installation To: beginners@haskell.org Message-ID: 31f41061-3886-4356-a3d1-6ed3499a1...@friendlyvirus.org Content-Type: text/plain;
Beginners Digest, Vol 47, Issue 26
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: problems with wxHaskell installation (Miguel Negrao) 2. Re: problems with wxHaskell installation (Brandon Allbery) 3. Re: How to solve this using State Monad? (Ertugrul S?ylemez) 4. Re: problems with wxHaskell installation (Miguel Negrao) 5. Re: How to solve this using State Monad? (Ozgur Akgun) 6. State and GUI's / external interfaces / events (Henry Lockyer) -- Message: 1 Date: Mon, 28 May 2012 20:20:21 +0100 From: Miguel Negrao miguel.negrao-li...@friendlyvirus.org Subject: Re: [Haskell-beginners] problems with wxHaskell installation To: beginners@haskell.org Message-ID: 8e5a9b9e-b6d9-441c-b9b8-76222be11...@friendlyvirus.org Content-Type: text/plain; charset=windows-1252 A 28/05/2012, ?s 19:44, Heinrich Apfelmus escreveu: Miguel Negrao wrote: When I try to install wx after updating cabal it is failing on version 0.90..0.1: miguelnegrao@Mac-Miguel:~$ cabal install wx Resolving dependencies... Configuring wx-0.90.0.1... Preprocessing library wx-0.90.0.1... Building wx-0.90.0.1... [ 1 of 16] Compiling Graphics.UI.WX.Types ( src/Graphics/UI/WX/Types.hs, dist/build/Graphics/UI/WX/Types.o ) [ 2 of 16] Compiling Graphics.UI.WX.Attributes ( src/Graphics/UI/WX/Attributes.hs, dist/build/Graphics/UI/WX/Attributes.o ) [ 3 of 16] Compiling Graphics.UI.WX.Layout ( src/Graphics/UI/WX/Layout.hs, dist/build/Graphics/UI/WX/Layout.o ) [ 4 of 16] Compiling Graphics.UI.WX.Classes ( src/Graphics/UI/WX/Classes.hs, dist/build/Graphics/UI/WX/Classes.o ) [ 5 of 16] Compiling Graphics.UI.WX.Media ( src/Graphics/UI/WX/Media.hs, dist/build/Graphics/UI/WX/Media.o ) [ 6 of 16] Compiling Graphics.UI.WX.Events ( src/Graphics/UI/WX/Events.hs, dist/build/Graphics/UI/WX/Events.o ) [ 7 of 16] Compiling Graphics.UI.WX.Window ( src/Graphics/UI/WX/Window.hs, dist/build/Graphics/UI/WX/Window.o ) src/Graphics/UI/WX/Window.hs:134:52: Not in scope: `textCtrlChangeValue' cabal: Error: some packages failed to install: wx-0.90.0.1 failed during the building phase. The exception was: ExitFailure 1 Does this mean that the package that was pushed to cabal has an actual error ? How do I use the latest patch level releases? of the packages ? Jeremy forgot to narrow the version dependencies of the family of wx packages, not every combination that cabal accepts will actually work. The effect is that you have to reinstall the packages in the right order and with the right version number to get it to work. The following should do the trick cabal install wxdirect-0.90.0.1 cabal install wxc-0.90.0.3 cabal install wxcore-0.90.0.1 cabal install wx-0.90.0.1 The last number in the version number indicates bug fixes, that's why I refer to it as patch-level?. Ah, ok. I ran all those commands, but with --reinstall since some were already installed, in that order. Everything installed correctly. Now when I try to compile a hello world program * I get : ghc test.hs [1 of 1] Compiling Main ( test.hs, test.o ) Linking test ... ld: warning: ignoring file /System/Library/Frameworks//QuickTime.framework/QuickTime, file was built for unsupported file format which is not the architecture being linked (x86_64) ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame Undefined symbols for architecture x86_64: _wxListItemAttr_CreateEx, referenced from: _sUn6_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _sUng_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListItemAttr_Create, referenced from: _wxcorezm0zi90zi0zi1_GraphicsziUIziWXCoreziWxcClassesAL_listItemAttrCreate1_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListCtrlVirtual_CreateWithCb, referenced from: _sW0i_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _sW0E_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListCtrlVirtual_Create, referenced from: _sWbY_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _sWcg_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListItemAttr_SetTextColour, referenced from: _s15xV_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListItemAttr_SetFont, referenced from: _s15BK_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _s15BO_info in libHSwxcore-0.90.0.1.a(WxcClassesAL.o) _wxListItemAttr_SetBackgroundColour, referenced from: _s15Gu_info in
Beginners Digest, Vol 47, Issue 28
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Today's Topics:
1. Re: Category question (Manfred Lotz)
2. monad transformer show help (rickmurphy)
3. Re: monad transformer show help (Tobias Brandt)
4. Re: Category question (Brent Yorgey)
5. Re: Category question (Manfred Lotz)
6. Re: State and GUI's / external interfaces / events
(Henry Lockyer)
--
Message: 1
Date: Tue, 29 May 2012 13:42:39 +0200
From: Manfred Lotz manfred.l...@arcor.de
Subject: Re: [Haskell-beginners] Category question
To: beginners@haskell.org
Message-ID: 20120529134239.4a518...@arcor.com
Content-Type: text/plain; charset=US-ASCII
On Mon, 28 May 2012 13:43:33 -0400 (EDT)
Jay Sulzberger j...@panix.com wrote:
No. The point is that, by definition, a category, call it C, is
a struct with two sets, Obj(C) and Mor(C), and further operations:
1. head: Mor(C) - Obj(C)
2. tail: Mor(C) - Obj(C)
3. id: Obj(C) - Mor(C)
4. *: Mor(C) x Mor(C) - Mor(C)
where head and tail and id are everywhere defined single valued
maps. They are all maps of sets. *, read composition of
morphisms is a map of sets, with signature as displayed, but is
not usually everywhere defined. We have then several
equational axioms, which C is required to satisfy to be a
category.
(set theoretical note: We have, partly implicitly, ruled out
categories which are not small. See standard texts for this
locus of difficulty.)
By the axioms, any object b of C must have defined its associated
identity morphism id[b]. For many categories, b will always be
an actual set, and id[b] will be the unique map of sets defined
by
(id[b])(x) = x , for all x in b
where (id[b])(x) is read the result of applying id[b] to the element
x of b.
But, as explained, many categories have objects which are not
sets. Indeed, often, no object is a set.
The definition of category never mentions whether or not the
objects are sets. And, as we have seen, there are many
categories whose objects are not sets. (Perhaps categorically
better: many categories are not directly presented as having
objects which are sets.)
to repeat: The concept category is larger in extension than the
concept category whose objects are sets and whose morphisms are
maps of sets.
ad representations of categories:
http://en.wikipedia.org/wiki/Yoneda_Lemma
[page was last modified on 1 April 2012 at 05:17]
I guess that this made me think of idA as idA(x) = x for each x of
A. Later when I saw other (more general) definitions I did not read
carefully to realize the difference.
Thanks a lot for making this clear to me.
--
Manfred
I will let stand my restatement of what you already know ;)
oo--JS.
Thanks a lot for the detailed example and explanations. I will study
your post thoroughly.
--
Manfred
--
Message: 2
Date: Tue, 29 May 2012 08:35:29 -0400
From: rickmurphy r...@rickmurphy.org
Subject: [Haskell-beginners] monad transformer show help
To: beginners beginners@haskell.org
Message-ID: 1338294929.2302.20.camel@metho-laptop
Content-Type: text/plain; charset=UTF-8
Hello All:
Over the past few days I got my first exposure to monad transformers.
I worked through the sample below.
The witness w displays IC 0 as expected, but even after providing the
instance of show for type O I a, witness w' causes ghci to display
No instance for (Num (I' a0))
arising from a use of w'
Possible fix: add an instance declaration for (Num (I' a0))
Would someone be able to explain why after providing the instance of
show on O I a, w' does not print the expected result (OC (IC 0)) ?
BTW - You will notice the sample intentionally avoids the use of
deriving (Show) on newtype I.
--
Rick
{-# LANGUAGE NoMonomorphismRestriction, DatatypeContexts,
FlexibleContexts, FlexibleInstances #-}
module Main where
import Control.Monad
import Control.Monad.Trans.Class
snip
-- |A parameterized new type I representing an inner type with one
constructor IC
newtype I a = IC a -- deriving (Show)
-- |Unwraps the value in the inner type
unI (IC x) = x
-- |A monad instance on the inner type
instance Monad I where
return = IC
m = f = f (unI m)
instance Show a = Show (I a) where
show (IC x) = IC ++ show x
-- |Witness on inner type
w :: Num a = I a
w = (IC 0) = return . id
-- |A parameterized new type O m a representing an outer type with a
named constructor
Beginners Digest, Vol 47, Issue 29
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Performance problem (Jefferson Andrade) 2. Performance problem (Rados?aw Szymczyszyn) -- Message: 1 Date: Wed, 30 May 2012 02:03:32 -0300 From: Jefferson Andrade joandr...@gmail.com Subject: [Haskell-beginners] Performance problem To: beginners@haskell.org Message-ID: ca+u7k5gg7vr5_+we1hwonbjjpslcakb0snxtsr7qu51-utn...@mail.gmail.com Content-Type: text/plain; charset=utf-8 Hi! I have a basic knowledge about Haskell and I am trying to put this knowledge to work with a few exercises. The one I am trying now is basically the following. 1. I must read from the standard input a series of text lines. Each line represents a command that must be performed. The possible commands are: add id first-name last-name birth-date phone-number del id info id query (key:value)+ 2. Each command may or may not generate an output on the standard output according to a series of conditions (if an entry with the same ID already exists, if the id of a del does not exists, if the id of an info does not exists). Also, the info and query command also generate output on the normal working. 3. The program is working, I suppose, but when I submit it for testing and ranking on spoj.pl I get a timeout. The maximum allowed time for this problem is 6s. My code is the following: = Begin of source code = -- Problem id: HASHADQI import qualified Data.List as List import qualified Data.IntMap as Map import Data.Maybe type Person = (String,String,String,String) type IntPersonMap = Map.IntMap Person main = do input - getContents seqAction Map.empty $ lines input seqAction :: IntPersonMap - [String] - IO IntPersonMap seqAction m [] = return m seqAction m (l:ls) = do m' - doAction m l seqAction m' ls doAction :: IntPersonMap - String - IO IntPersonMap doAction m cmd = do case cmd of 'a':cs - doInsert m (words cmd) 'd':cs - doDelete m (words cmd) 'i':cs - doInfo m (words cmd) 'q':cs - doQuery m (words cmd) [] - return m doInsert :: IntPersonMap - [String] - IO IntPersonMap doInsert m [_, idText, fn, ln, bd, pn] = do let id = read idText :: Int if Map.member id m then do putStrLn $ ID ++ show id ++ ja cadastrado. return m else return (Map.insert id (fn, ln, bd, pn) m) doDelete :: IntPersonMap - [String] - IO IntPersonMap doDelete m [_, idText] = do let id = read idText :: Int if Map.member id m then return (Map.delete id m) else do putStrLn $ ID ++ show id ++ nao existente. return m doInfo :: IntPersonMap - [String] - IO IntPersonMap doInfo m [_, idText] = do let id = read idText :: Int case Map.lookup id m of Just (fn, ln, bd, pn) - do putStrLn $ unwords [fn, ln, bd, pn] return m Nothing - do putStrLn $ ID ++ show id ++ nao existente. return m doQuery :: IntPersonMap - [String] - IO IntPersonMap doQuery m (_:qs) = do let test = (\x - foldl () True $ map ($x) $ makePredicate qs) result = Map.filter test m putStrLn $ unwords . map show $ Map.keys result return m makePredicate :: [String] - [(Person - Bool)] makePredicate [] = [] makePredicate (q:qs) = case List.break (==':') q of (fn, ':':x) - (\(fn,_,_,_) - fn == x) : (makePredicate qs) (ln, ':':x) - (\(_,ln,_,_) - ln == x) : (makePredicate qs) (bd, ':':x) - (\(_,_,bd,_) - bd == x) : (makePredicate qs) (pn, ':':x) - (\(_,_,_,pn) - pn == x) : (makePredicate qs) = End of source code = Can any one explain where is the source(s) of inefficiency and suggest how to make this program more efficient? Thanks in advance, Jeff. -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120530/80fe29f1/attachment-0001.htm -- Message: 2 Date: Wed, 30 May 2012 11:07:22 +0200 From: Rados?aw Szymczyszyn lav...@gmail.com Subject: [Haskell-beginners] Performance problem To: beginners@haskell.org Message-ID: CAG=dco2ff0z83+g+tvhjrpw1uwu066zr4pa0y5-ga+ordvr...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Hello! I've had a similar problem with text processing discussed on the list some time ago (a topic about implementing a spellchecker). To keep things short'n'simple: built-in Haskell Strings are inefficient as they're simply lists of Chars, i.e. a String is in fact just a [Char]. The usually suggested
Beginners Digest, Vol 47, Issue 31
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Today's Topics:
1. Re: How to solve this using State Monad? (Henry Lockyer)
2. Re: How to solve this using State Monad? (kak dod)
--
Message: 1
Date: Wed, 30 May 2012 16:14:35 +0100
From: Henry Lockyer henry.lock...@ntlworld.com
Subject: Re: [Haskell-beginners] How to solve this using State Monad?
To: beginners@haskell.org
Message-ID: 463edfbf-a1d5-4436-a37b-708e2a5e9...@ntlworld.com
Content-Type: text/plain; charset=us-ascii
I should have gone back and cleaned up my original 'Version 1' example so that
both examples use exactly the same 'stateMC' function.
I have now made this small improvement below FWIW.
/Henry
On 30 May 2012, at 15:31, Henry Lockyer wrote:
Hi kak,
On 28 May 2012, at 19:49, kak dod wrote:
Hello,
A very good morning to all.
I am a Haskell beginner. And although I have written fairly complicated
programs and have understood to some extent the concepts like pattern
matching, folds, scans, list comprehensions, but I have not satisfactorily
understood the concept of Monads yet. I have partially understood and used
the Writer, List and Maybe monads but the State monad completely baffles me.
I wanted to write a program for the following problem: A DFA simulator.
This I guess is a right candidate for State monad as it mainly deals with
state changes.
What the program is supposed to do is:
. . .
I wrote a recursive program to do this without using any monads. I simply
send the entire dfa, the input string and its partial result in the
recursive calls.
How to do this using State Monad?
. . .
Please note that I wish your solution to use the Control.Monad.State.
I coincidentally included something like this in another post I recently
made.
I have quickly tweaked my example slightly and added a complete alternative
example using the State monad below.
Both programs now have the same external behaviour.
It is a simpler example than the DFA that you are proposing. If I have time
I'll look at your specific version of
the problem, but I am assuming that your main aim here is to understand the
State monad better - rather than the DFA
exactly as you have specified it - so perhaps the following simple examples
may help a little:
---
--
-- aha!
--
-- An exciting game that requires the string aha! to
-- be entered in order to reach the exit, rewarded with a *.
--
-- A simple state machine.
--
-- Version 1 - not using the State monad...
--
import System.IO
type MyState = Char
initstate, exitstate :: MyState
initstate = 'a'
exitstate = 'z'
main = do hSetBuffering stdin NoBuffering -- (just so it responds char by
char on the terminal)
stateIO initstate
stateIO :: MyState - IO ()
stateIO s = do c_in - getChar
let (str_out, s') = stateMC' c_in s
putStr str_out -- (newline flushes the output)
stateIO s'
-- now uses exactly the same stateMC func as in version 2 below...
-- ('Y' = Yes, 'N' = No, '*' = congratulations game over, blank responses after
game over)
stateMC' :: Char - MyState - (String, MyState)
stateMC' 'a' 'a' = ( Y\n, 'b')
stateMC' 'h' 'b' = ( Y\n, 'c')
stateMC' 'a' 'c' = ( Y\n, 'd')
stateMC' '!' 'd' = ( *\n, 'z')
stateMC' _ 'z' = ( \n, 'z')
stateMC' _ _ = ( N\n, 'a')
--
-- Version 2 - using the State monad...
-- This time it treats the input as one long lazy String of chars
-- rather than char-by-char reading as in version 1
--
import System.IO
import Control.Monad.State
type MyState = Char
initstate, exitstate :: MyState
initstate = 'a'
exitstate = 'z'
main = do hSetBuffering stdin NoBuffering
interact mystatemachine
mystatemachine :: String - String
mystatemachine str = concat $ evalState ( mapM charfunc str ) initstate
charfunc :: Char - State MyState String
charfunc c = state $ stateMC' c -- wrap the stateMC' func in the state
monad
snip - remove previous comment
stateMC' :: Char - MyState - (String, MyState)
stateMC' 'a' 'a' = ( Y\n, 'b')
stateMC' 'h' 'b' = ( Y\n, 'c')
stateMC' 'a' 'c' = ( Y\n, 'd')
stateMC' '!' 'd' = ( *\n, 'z')
stateMC' _ 'z' = ( \n, 'z')
stateMC' _ _ = ( N\n, 'a')
-
Advantages of using
Beginners Digest, Vol 47, Issue 33
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: How to solve this using State Monad? (Henry Lockyer) 2. Re: How to solve this using State Monad? (Ertugrul S?ylemez) 3. Re: How to solve this using State Monad? (Michael Alan Dorman) -- Message: 1 Date: Thu, 31 May 2012 11:58:47 +0100 From: Henry Lockyer henry.lock...@ntlworld.com Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: kak dod kak.dod2...@gmail.com Cc: beginners@haskell.org, Ertugrul S?ylemez e...@ertes.de Message-ID: a38a2cbe-70dd-4832-a021-c44f11574...@ntlworld.com Content-Type: text/plain; charset=iso-8859-1 Hi kak - ok, my mistake - I interpreted your candidate for the state monad, and Please note that I wish your solution to use the Control.Monad.State too literally. Arrows may point the way forward for you then ;-) I have a suspicion that if the State monad doesn't make sense yet, then Arrows will not be more obvious, they look like a kind of more generalised monadic structure (though I don't understand them myself yet) - but maybe a better fit to your problem will in fact make them clearer for you. Regarding the State monad: I think it may be slightly unfortunate that it gets introduced as THE state monad (I guess Ertugrul may agree here...) and the initial examples, like the favourite random number generation example, do not make it immediately obvious how you might apply it more widely. I certainly experienced a little head-scratching before realising I could simply use things like charfunc c = state (stateMC c). Another thing that can cause some initial confusion is the fact that the standard implementation seems to have changed since some of the educational texts were written, so you may find yourself in Hoogle looking at monad transformers before you feel quite ready for them ;-) Also the standard solution does not export the value constructor so, unlike some examples that you may see, you can only use State for type definitions and you need to use state to create an actual value. I think it is a good idea, as Ertugrul suggested, to write your own state monad instance, and it avoids these 'noise factors' from the library implem. /Henry On 31 May 2012, at 05:29, kak dod wrote: Hello Ertugrul, Thank you very much for your patience with a stupid like me. I am going through your comments, part of it is going parallel but I am getting something. Sorry for that. But I am bit confused with the purpose of State Monad now. Is the name State Monad appropriate to this monad? I mean, if it is appropriate then the State Monad must be useful to model all types of computations involving state as a dominant part. Am I making a mistake here? I guess, I am. Because it seems from what you have said that the State Monad is appropriate only for some types of computations involving state and not appropriate for something like DFA which I think is a stateful computation. What I am trying to do is write a Turing Machine simulator in Haskell? It's also mainly a state change thing, so if Ertugrul says that State Monad is not suitable for DFA simulation, it won't be suitable for TM simulation either. So, exactly what type of computations involving what type of states are better handled by the State Monad? I mean what type of state-computations can be made composible using the State Monad and what type of state-computations cannot be made composible using the State Monad? (As you have pointed out automaton cannot be made composible using the State Monad in an elegant manner.) Thanks Henry for your example, it has helped me a lot. On Thu, May 31, 2012 at 6:12 AM, Henry Lockyer henry.lock...@ntlworld.com wrote: I hear you Ertugrul ;-) I interpret that kak is struggling to understand the State monad, not find the best solution for a DFA, so telling him about something else which is not the State monad will probably not help him too much at this point... Your propaganda is working on me though ! :-) I haven't looked at the arrows area at all so far, but I'm interested in state handling solutions so I see I need to move it up my reading list! Thanks/ Henry On 30 May 2012, at 23:25, Ertugrul S?ylemez wrote: Again to promote the automaton arrow, Henry's aha! DFA in the automaton arrow: aha :: Auto Char Char aha = aha' 0 where aha' :: Int - Auto Char Char
Beginners Digest, Vol 47, Issue 34
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: How to solve this using State Monad? (Miguel Negrao) 2. Re: How to solve this using State Monad? (Ertugrul S?ylemez) 3. Re: How to solve this using State Monad? (Henry Lockyer) 4. GHCi won't allow type declaration as shown inLYAHFGG (Stan Kulp) 5. Re: GHCi won't allow type declaration as shown in LYAHFGG (Homero Cardoso de Almeida) 6. Re: GHCi won't allow type declaration as shown in LYAHFGG (Brandon Allbery) -- Message: 1 Date: Thu, 31 May 2012 16:46:26 +0100 From: Miguel Negrao miguel.negrao-li...@friendlyvirus.org Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: 9c2c6f14-1233-49cc-a346-b48140a6d...@friendlyvirus.org Content-Type: text/plain; charset=windows-1252 A 31/05/2012, ?s 16:25, Michael Alan Dorman escreveu: Ertugrul S?ylemez e...@ertes.de writes: I almost feel stupid writing these long explanations, just to see them getting ignored ultimately. The automaton arrow is one of the most useful and most underappreciated concepts for state in Haskell. While I'm not sure I have a need for it right now, I definitely haven't ignored this exchange---I've read the individual emails, and a link to the archive is filed away for future use. So it's been very helpful, even if those being helped aren't participating per se. +1 Because of those posts I spent my morning reading about arrows which seems a quite interesting concept, although couldn?t yet see what is best for ( I would be curious to learn it in order to try out Yampa). I have to say that the resources I found to learn about arrows on the net were a bit disorganized. This page is really well done http://en.wikibooks.org/wiki/Haskell/Understanding_arrows but then because I don?t know much about parsers I couldn?t really progress through the second half. best, Miguel Negr?o -- Message: 2 Date: Thu, 31 May 2012 18:18:07 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: 20120531181807.37bed...@tritium.streitmacht.eu Content-Type: text/plain; charset=utf-8 Miguel Negrao miguel.negrao-li...@friendlyvirus.org wrote: Because of those posts I spent my morning reading about arrows which seems a quite interesting concept, although couldn?t yet see what is best for ( I would be curious to learn it in order to try out Yampa). I have to say that the resources I found to learn about arrows on the net were a bit disorganized. This page is really well done http://en.wikibooks.org/wiki/Haskell/Understanding_arrows but then because I don?t know much about parsers I couldn?t really progress through the second half. I have started an arrow tutorial which many people found easy to follow. It's not finished yet, but since so many people found it useful I'm sharing that unfinished tutorial: http://ertes.de/new/tutorials/arrows.html It answers the most important questions: What? Why? How? To some extent it also answers: When? But I have to work on that question. The basics of the automaton arrow are covered, but when I find time I will extend the tutorial to cover Auto in full. Finally I also intend to cover a powerful generalization of Auto: the wire arrow, which is the basis of the Netwire AFRP library. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife = sex) http://ertes.de/ -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120531/709e5178/attachment-0001.pgp -- Message: 3 Date: Thu, 31 May 2012 17:23:08 +0100 From: Henry Lockyer henry.lock...@ntlworld.com Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: 41b1172f-bfa0-450e-adf9-b74fe4adf...@ntlworld.com Content-Type: text/plain; charset=windows-1252 + I think I already said it, but, in case it was not clear: Me too. Even as a participating person I feel helped! ;-) I just haven't taken it onboard yet and need that quiet free morning to read more about it... + I think this is clearly identifying the point where the State monad(s) can become confusing at first, in my (limited) experience:
Beginners Digest, Vol 48, Issue 1
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: GHCi won't allow type declaration as shown in LYAHFGG (Keshav Kini) 2. Re: GHCi won't allow type declaration as shown in LYAHFGG (Homero Cardoso de Almeida) 3. Re: How to solve this using State Monad? (Rustom Mody) -- Message: 1 Date: Thu, 31 May 2012 14:16:04 -0700 From: Keshav Kini keshav.k...@gmail.com Subject: Re: [Haskell-beginners] GHCi won't allow type declaration as shown in LYAHFGG To: beginners@haskell.org Message-ID: 86r4u09hm3@zhenghe.ntu.edu.sg Content-Type: text/plain; charset=us-ascii Stan Kulp stan_k...@yahoo.com writes: I have been working my way through Learn You a Haskell for Greater Good and am stumped when I get to the Syntax in Functions - Pattern Matching section. The book shows the following expression... ghci lucky :: (Integral a) = a - String As far as I can see, the live version of `the section you mention`_ on learnyouahaskell.com does not contain this text - it doesn't have the ghci at the beginning of the line. Besides what others have said in response to your question, I would add that you should make sure to read LYAH on the website if possible - other sources might be out of date, as I think the author does update the website version from time to time. .. _the section you mention: http://learnyouahaskell.com/syntax-in-functions#pattern-matching -Keshav -- Message: 2 Date: Thu, 31 May 2012 19:45:56 -0300 From: Homero Cardoso de Almeida homero...@gmail.com Subject: Re: [Haskell-beginners] GHCi won't allow type declaration as shown in LYAHFGG To: Keshav Kini keshav.k...@gmail.com Cc: beginners@haskell.org Message-ID: capv0zwq_sw2lx+dndv3osm8ijjopqzcgk9s4w8yfwdpbi86...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I just tried here, and got no problems. lucky.hs: lucky :: (Integral a) = a - String lucky 7 = LUCKY NUMBER SEVEN!!! lucky x = Sorry, you're out of luck, pal... ghci: :load /path/to/lucky.hs [1 of 1] Compiling Main ( /path/to/lucky.hs, interpreted ) Ok, modules loaded: Main. *Main lucky 7 LUCKY NUMBER SEVEN!!! *Main lucky 200 Sorry, you're out of luck, pal... *Main I would suggest verifying my ghc installation or for any funky chars in the file. Homero Cardoso de Almeida On Thu, May 31, 2012 at 6:16 PM, Keshav Kini keshav.k...@gmail.com wrote: Stan Kulp stan_k...@yahoo.com writes: I have been working my way through Learn You a Haskell for Greater Good and am stumped when I get to the Syntax in Functions - Pattern Matching section. The book shows the following expression... ghci lucky :: (Integral a) = a - String As far as I can see, the live version of `the section you mention`_ on learnyouahaskell.com does not contain this text - it doesn't have the ghci at the beginning of the line. Besides what others have said in response to your question, I would add that you should make sure to read LYAH on the website if possible - other sources might be out of date, as I think the author does update the website version from time to time. .. _the section you mention: http://learnyouahaskell.com/syntax-in-functions#pattern-matching -Keshav ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120531/97815794/attachment-0001.htm -- Message: 3 Date: Fri, 1 Jun 2012 08:58:01 +0530 From: Rustom Mody rustompm...@gmail.com Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: Ertugrul S?ylemez e...@ertes.de Cc: beginners@haskell.org Message-ID: caj+teof7fz-tmoctfxcpknep54+i96+fwjtcsxzi47ppyq4...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 On Thu, May 31, 2012 at 9:48 PM, Ertugrul S?ylemez e...@ertes.de wrote: I have started an arrow tutorial which many people found easy to follow. It's not finished yet, but since so many people found it useful I'm sharing that unfinished tutorial: http://ertes.de/new/tutorials/arrows.html It answers the most important questions: What? Why? How? To some extent it also answers: When? But I have to work on that question. Hi Ertugrul, As usual this is useful and I'll be studying it in more
Beginners Digest, Vol 48, Issue 5
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: attoparsec and EOF (Arthur Clune) 2. Re: attoparsec and EOF (Arthur Clune) 3. Re: histogram over large data (Rados?aw Szymczyszyn) 4. Re: histogram over large data (Stephen Tetley) 5. Re: histogram over large data (Ian Knopke) 6. graphics.gloss errors (Gregory Guthrie) 7. wxHaskell install errors (Gregory Guthrie) 8. Re: graphics.gloss errors (Brent Yorgey) 9. Re: graphics.gloss errors (Gregory Guthrie) 10. Re: histogram over large data (Stephen Tetley) -- Message: 1 Date: Tue, 5 Jun 2012 15:29:03 +0100 From: Arthur Clune art...@clune.org Subject: Re: [Haskell-beginners] attoparsec and EOF To: beginners@haskell.org Message-ID: CAAa4kjx1T=oMqhFL+a4vzxR61nUea0ETWP+iyX=ozkqnj8o...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 And to answer my own question.I should use parseOnly. -- Arthur Clune art...@clune.org On Tue, Jun 5, 2012 at 10:56 AM, Arthur Clune art...@clune.org wrote: I'm writing a simple attoparsec parser, which works fine except for handling end of file: -- Message: 2 Date: Tue, 5 Jun 2012 15:42:55 +0100 From: Arthur Clune art...@clune.org Subject: Re: [Haskell-beginners] attoparsec and EOF To: beginners@haskell.org Message-ID: CAAa4kjw0UpB9SFDfGWThaQRPbVW-w7obELuY=qe=dkiubfr...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 And to answer my own question.I should use parseOnly. -- Arthur Clune art...@clune.org On Tue, Jun 5, 2012 at 10:56 AM, Arthur Clune art...@clune.org wrote: I'm writing a simple attoparsec parser, which works fine except for handling end of file: -- Message: 3 Date: Tue, 5 Jun 2012 20:41:42 +0200 From: Rados?aw Szymczyszyn lav...@gmail.com Subject: Re: [Haskell-beginners] histogram over large data To: beginners@haskell.org Message-ID: CAG=dco3qq++adaxfrytifr0r5qfesc3gsjhghiefzabsheu...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Hi Ian, In case you were looking for an example to get your teeth into you might be interested in these: https://gist.github.com/287 These two scripts both serve the same purpose of building a map of word counts from a text file. They both use Data.Text for Unicode IO, but each tests a different structure. Though unordered-containers package with its Data.HashMap is often suggested as an efficient mapping structure, in my case (of these two scripts) the Data.HashTable from standard library wins taking circa half the time to run on the same dataset (though it's not purely functional as its actions operate in the IO monad). Finally, what puzzles me the most, is that a roughly equivalent script in Python which just reads the same datafile into a standard dict performs in about 1/3 of the time of the faster one of the above two and Python's hardly a fast language... Bewildering, indeed. Hope I didn't put you off :) -- Message: 4 Date: Tue, 5 Jun 2012 21:06:00 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] histogram over large data To: Rados?aw Szymczyszyn lav...@gmail.com Cc: beginners@haskell.org Message-ID: CAB2TPRBR9c5b3X5K7aaaHp5sOgJ8TZUeEnkmqSjU83zmJ2f=l...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On 5 June 2012 19:41, Rados?aw Szymczyszyn lav...@gmail.com wrote: Finally, what puzzles me the most, is that a roughly equivalent script in Python which just reads the same datafile into a standard dict performs in about 1/3 of the time of the faster one of the above two and Python's hardly a fast language... Bewildering, indeed. Dicts are efficient in Python though (as they are efficiently implemented in C). Python often seems to beat Haskell in micro-benchmarks that just fill a dictionary then run a simple query / summation on it. -- Message: 5 Date: Tue, 5 Jun 2012 21:09:49 +0100 From: Ian Knopke ian.kno...@gmail.com Subject: Re: [Haskell-beginners] histogram over large data To: Stephen Tetley stephen.tet...@gmail.com Cc: beginners@haskell.org Message-ID: cac+f4wmk3kovxddjqth79w8diftaqufm3azovlnxmk25pme...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi Stephen, I see now I didn't explain myself especially well. One way to build a frequency count in haskell comes from LYAHFGG, chapter 7: ghci map (\l@(x:xs) - (x,length l)) . group .
Beginners Digest, Vol 48, Issue 7
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: flatten comma operator (Arlen Cuss) 2. Re: wrapping text in a multiline string (Rico Moorman) 3. Re: flatten comma operator (Kees Bleijenberg) 4. Re: wrapping text in a multiline string (Arlen Cuss) 5. Re: wxHaskell path (Miguel Negrao) -- Message: 1 Date: Wed, 6 Jun 2012 16:42:52 +1000 From: Arlen Cuss a...@unnali.com Subject: Re: [Haskell-beginners] flatten comma operator To: Kees Bleijenberg k.bleijenb...@inter.nl.net Cc: beginners@haskell.org Message-ID: bd4727d194e842a39621f06d81389...@unnali.com Content-Type: text/plain; charset=utf-8 By the way, is the excerpt from RWH involving liftA2 the chapter on using Parsec? If so, this may be the code snippet you refer to: -- file: ch16/FormApp.hs a_pair :: CharParser () (String, Maybe String) a_pair = liftA2 (,) (many1 a_char) (optionMaybe (char '=' * many a_char)) In this case, liftA2 is promoting the (,) operation to work with the two operations in the CharParser applicative functor. (,) is of type a - b - (a,b), so without lifting, we'd end up with something like (CharParser () String, CharParser () Maybe String) (just a guess here). liftA2 produces a new applicative functor action which computes each of (many1 a_char) and (optionMaybe (char '=' * many a_char)), then gives the pure results to (,). On Wednesday, 6 June 2012 at 4:36 PM, Arlen Cuss wrote: If (,) is a function that takes two elements and returns the 2-tuple, have you considered something like (,,)? :) On Wednesday, 6 June 2012 at 4:33 PM, Kees Bleijenberg wrote: In 'Real World Haskell' I found code like LiftA2 (,) Looks odd. But after some experimenting in winghci I found that (,) 1 2 is valid code and is equal to (1,2). Now I wonder how to create (1,2,3). I think you need a join or a flatten function or ...? Join doesn't work? Kees ___ Beginners mailing list Beginners@haskell.org (mailto:Beginners@haskell.org) http://www.haskell.org/mailman/listinfo/beginners -- Message: 2 Date: Wed, 6 Jun 2012 08:52:44 +0200 From: Rico Moorman rico.moor...@gmail.com Subject: Re: [Haskell-beginners] wrapping text in a multiline string To: Arlen Cuss a...@unnali.com Cc: beginners@haskell.org Message-ID: cajrzcx1qybl8pdqck1-bkf7by8ovewzkaxxfheghosbwrch...@mail.gmail.com Content-Type: text/plain; charset=windows-1252 Thank you very much for this suggestion. I just tried the character class you mentioned and it works. The stackoverflow post you mentioned was a nice read and I surely agree that regular expressions are normally not the way to go for most HTML munging needs. But luckily the generated HTML from pandoc is very specific and the table tag I wanted to match (for line-numbered code listings) does not contain any further tables so I thought it should be safe to approach it like this. The resulting code is now: -- Wraps numbered code listings within the page body with a div -- in order to be able to apply some more specific styling. wrapNumberedCodelistings (Page meta body) = Page meta newBody where newBody = regexReplace table\\s+class=\sourceCode[^]+[\\s\\S]*?/table wrap body wrap x = div class=\sourceCodeWrap\ ++ x ++ /div -- Replaces the whole match for the given regex using the given function regexReplace :: String - (String - String) - String - String regexReplace regex replace text = go text where go text = case text =~~ regex of Just (before, match, after) - before ++ replace match ++ go after _ - text Don't know though if it could be cleaned up further or even if this is by any means good style (being still fairly new to haskell). Furthermore I would still be very interested in the right approach to manipulating the HTML structure as a whole and I too hope that another Haskeller could name a more suitable solution for manipulating HTML. Or even how to pass the 's' modifier to Text.Regex.PCRE. Best regards, rico On Wed, Jun 6, 2012 at 7:11 AM, Arlen Cuss a...@unnali.com wrote: I'd be more inclined to look at a solution involving manipulating the HTML structure, rather than trying a regexp-based approach, which will probably end up disappointing. (See this: http://stackoverflow.com/a/1732454/499609 ) I hope another Haskeller can speak to a library that would be good for
Beginners Digest, Vol 48, Issue 8
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wrapping text in a multiline string (Rico Moorman) -- Message: 1 Date: Wed, 6 Jun 2012 10:39:28 +0200 From: Rico Moorman rico.moor...@gmail.com Subject: Re: [Haskell-beginners] wrapping text in a multiline string To: Arlen Cuss a...@unnali.com Cc: beginners@haskell.org Message-ID: CAJrzcX2-CSesYFfqFOGUSmDebYt3frrmJbT8_sy_792oMq=P=w...@mail.gmail.com Content-Type: text/plain; charset=windows-1252 Thank you again! Looking at the docs it seems that this could do the trick. A pity that you cannot install the package. Now I am wondering how I would integrate this in the replacement function or how to rewrite it properly. Looking at the type signature of =~~ (with my limited knowledge) it seems that I would have to use RegexMaker adding up the CompOptions needed? (=~~)?:: (RegexMaker?Regex?CompOption?ExecOption?source,?RegexContext Regex?source1 target,?Monad?m) = source1 - source - m target On Wed, Jun 6, 2012 at 9:46 AM, Arlen Cuss a...@unnali.com wrote: Exploring the documentation for Text.Regex.PCRE, I've found CompOption: http://hackage.haskell.org/packages/archive/regex-pcre/0.94.4/doc/html/Text-Regex-PCRE-Wrap.html#t:CompOption The constants are listed below; the one you want is probably compDotAll, to make . match newlines as well. I'm not 100% sure if this is the module you want, though, and I can't seem to get regex-pcre installed, so I can't test. Apologies! On Wednesday, 6 June 2012 at 4:52 PM, Rico Moorman wrote: Thank you very much for this suggestion. I just tried the character class you mentioned and it works. The stackoverflow post you mentioned was a nice read and I surely agree that regular expressions are normally not the way to go for most HTML munging needs. But luckily the generated HTML from pandoc is very specific and the table tag I wanted to match (for line-numbered code listings) does not contain any further tables so I thought it should be safe to approach it like this. The resulting code is now: -- Wraps numbered code listings within the page body with a div -- in order to be able to apply some more specific styling. wrapNumberedCodelistings (Page meta body) = Page meta newBody where newBody = regexReplace table\\s+class=\sourceCode[^]+[\\s\\S]*?/table wrap body wrap x = div class=\sourceCodeWrap\ ++ x ++ /div -- Replaces the whole match for the given regex using the given function regexReplace :: String - (String - String) - String - String regexReplace regex replace text = go text where go text = case text =~~ regex of Just (before, match, after) - before ++ replace match ++ go after _ - text Don't know though if it could be cleaned up further or even if this is by any means good style (being still fairly new to haskell). Furthermore I would still be very interested in the right approach to manipulating the HTML structure as a whole and I too hope that another Haskeller could name a more suitable solution for manipulating HTML. Or even how to pass the 's' modifier to Text.Regex.PCRE. Best regards, rico On Wed, Jun 6, 2012 at 7:11 AM, Arlen Cuss a...@unnali.com (mailto:a...@unnali.com) wrote: I'd be more inclined to look at a solution involving manipulating the HTML structure, rather than trying a regexp-based approach, which will probably end up disappointing. (See this: http://stackoverflow.com/a/1732454/499609) I hope another Haskeller can speak to a library that would be good for this kind of purpose. To suit what you're doing now, though; if you change .*? to [\s\S]*?, it should work on multiline strings. If you can work out how to pass the 's' modifier to Text.Regexp.PCRE, that should also do it. ?Arlen On Wednesday, 6 June 2012 at 3:05 PM, Rico Moorman wrote: Hello, I have a given piece of multiline HTML (which is generated using pandoc btw.) and I am trying to wrap certain elements (tags with a given class) with a div. I already took a look at the Text.Regex.PCRE module which seemed a reasonable choice because I am already familiar with similar regex implementations in other languages. I came up with the following function which takes a regex and replaces all matches within the given string using the provided function (which I would use to wrap the element)
Beginners Digest, Vol 48, Issue 9
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: flatten comma operator (Brent Yorgey) 2. Re: flatten comma operator (Arlen Cuss) 3. Re: wrapping text in a multiline string (Arlen Cuss) 4. Re: wxHaskell path (Henry Lockyer) 5. Re: wxHaskell install errors (Heinrich Apfelmus) 6. Re: histogram over large data (Ben Gamari) -- Message: 1 Date: Wed, 6 Jun 2012 06:58:57 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] flatten comma operator To: beginners@haskell.org Message-ID: 20120606105857.ga17...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Wed, Jun 06, 2012 at 09:46:58AM +0200, Kees Bleijenberg wrote: This is indeed the code I was talking about. I did not understand how I could create (1,2,3) with the comma operator (,)((,) 1 2) 3 = ((1,2),3) and not (1,2,3). That's why I thought I needed a kind of join operation to 'flatten' this. It's not possible to create a triple using only the (,) operator -- there's no way to do the join/flatten operation you have in mind, because there's no valid type it could be assigned (unless you make it specific to three-tuples, but I'm guessing you have something more general in mind). Indeed (,,) 1 2 3 is (1,2,3). But I do not understand what is happening. Is (,,) predefined? Probably not. Yes, it is! -Brent -- Message: 2 Date: Wed, 6 Jun 2012 21:06:04 +1000 From: Arlen Cuss a...@unnali.com Subject: Re: [Haskell-beginners] flatten comma operator To: Kees Bleijenberg k.bleijenb...@inter.nl.net Cc: beginners@haskell.org Message-ID: c5d52883eeb84f3da1d3d38db8a9c...@unnali.com Content-Type: text/plain; charset=utf-8 On Wednesday, 6 June 2012 at 5:46 PM, Kees Bleijenberg wrote: This is indeed the code I was talking about. I did not understand how I could create (1,2,3) with the comma operator (,)((,) 1 2) 3 = ((1,2),3) and not (1,2,3). That's why I thought I needed a kind of join operation to 'flatten' this. As Brent pointed out, you can't without making it very specific. Each length of tuple with its combination of types is a unique type itself; compare to a list, where [a] is the type for a list of any length (including zero) containing elements of type a. A list is trivial to append to, whereas tuples are not designed for extension in this manner, per se. Indeed (,,) 1 2 3 is (1,2,3). But I do not understand what is happening. Is (,,) predefined? Probably not. And as Brent pointed out also, it is. :) By the way, so is (,,,)! I suspect GHC allows any number. The Haskell Report section 6.1.4 [1] says implementations must support up to at least 15. Cheers, Arlen [1] http://www.haskell.org/onlinereport/basic.html -Oorspronkelijk bericht- Van: Arlen Cuss [mailto:a...@unnali.com] Verzonden: woensdag 6 juni 2012 8:43 Aan: Kees Bleijenberg CC: beginners@haskell.org (mailto:beginners@haskell.org) Onderwerp: Re: [Haskell-beginners] flatten comma operator By the way, is the excerpt from RWH involving liftA2 the chapter on using Parsec? If so, this may be the code snippet you refer to: -- file: ch16/FormApp.hs a_pair :: CharParser () (String, Maybe String) a_pair = liftA2 (,) (many1 a_char) (optionMaybe (char '=' * many a_char)) In this case, liftA2 is promoting the (,) operation to work with the two operations in the CharParser applicative functor. (,) is of type a - b - (a,b), so without lifting, we'd end up with something like (CharParser () String, CharParser () Maybe String) (just a guess here). liftA2 produces a new applicative functor action which computes each of (many1 a_char) and (optionMaybe (char '=' * many a_char)), then gives the pure results to (,). On Wednesday, 6 June 2012 at 4:36 PM, Arlen Cuss wrote: If (,) is a function that takes two elements and returns the 2-tuple, have you considered something like (,,)? :) On Wednesday, 6 June 2012 at 4:33 PM, Kees Bleijenberg wrote: In 'Real World Haskell' I found code like LiftA2 (,) Looks odd. But after some experimenting in winghci I found that (,) 1 2 is valid code and is equal to (1,2). Now I wonder how to create (1,2,3). I think you need a join or a flatten function or ...?
Beginners Digest, Vol 48, Issue 10
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wxHaskell install errors (carlos gomez) 2. Re: wxHaskell install errors (Gregory Guthrie) 3. Re: wxHaskell install errors (Gregory Guthrie) 4. Re: graphics.gloss errors (Chadda? Fouch?) 5. Re: wrapping text in a multiline string (Chadda? Fouch?) 6. Re: wxHaskell install errors (carlos gomez) 7. Re: wrapping text in a multiline string (Rico Moorman) -- Message: 1 Date: Wed, 6 Jun 2012 12:38:37 -0400 From: carlos gomez carliro...@gmail.com Subject: Re: [Haskell-beginners] wxHaskell install errors To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org beginners@haskell.org Message-ID: cahg7derurgkleja8yhdgb73nymrpt8c7nvft2u5+brbkeea...@mail.gmail.com Content-Type: text/plain; charset=windows-1252 Is your wx-config working ? You can try: *wx-config ?help* If not, try with another, you can use these ones: - download from https://sites.google.com/site/wxconfig/sourcecode and compile with g++ wx-config.cpp -o wx-config.exe - or download directly the .exe from http://sourceforge.net/projects/wxhaskell/files/wx-config-win/ Regards, Carlos Gomez On 5 June 2012 16:23, Gregory Guthrie guth...@mum.edu wrote: I had all of the wxHaskell programs installed and working fine, but now with an update to Haskell Platform and thus also ghci, I need to upgrade all of them (the previously working programs fail) requiring an update for the underlying wxWidgets from 2.8 to 2.9 versions. I downloaded and built wxWidgets 2.9, since the current wxHaskell libraries require it (I couldn't find any existing binaries online). The compile seemed to be successful, but when I then try to use it from the wxHaskell programs I get an error that I don't know how to fix: C: cabal install wx Resolving dependencies... [1 of 1] Compiling Main ( C:\Users\guthrie\AppData\Local\Temp\wxc-0. 90.0.3-7324\wxc-0.90.0.3\Setup.hs, C:\Users\guthrie\AppData\Local\Temp\wxc-0.90. 0.3-7324\wxc-0.90.0.3\dist\setup\Main.o ) Linking C:\Users\guthrie\AppData\Local\Temp\wxc-0.90.0.3-7324\wxc-0.90.0.3\dist\ setup\setup.exe ... Configuring wxc-0.90.0.3... Configuring wxc to build against wxWidgets 2.9 setup.exe: Missing dependencies on foreign libraries: * Missing C libraries: wxmsw29ud_all, wxtiffd, wxjpegd, wxpngd, wxzlibd,wxregexud, wxexpatd, wxregexud This problem can usually be solved by installing the system packages that provide these libraries (you may need the -dev versions). If the libraries are already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where they are. cabal: Error: some packages failed to install: wx-0.90.0.1 depends on wxc-0.90.0.3 which failed to install. wxc-0.90.0.3 failed during the configure step. The exception was: ExitFailure 1 wxcore-0.90.0.1 depends on wxc-0.90.0.3 which failed to install. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120606/5f3a5106/attachment-0001.htm -- Message: 2 Date: Wed, 6 Jun 2012 11:42:58 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] wxHaskell install errors To: carlos gomez carliro...@gmail.com Cc: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01a2767cb...@mail.cs.mum.edu Content-Type: text/plain; charset=iso-8859-1 Thanks, yes - it seems good, it responds with a help menu message. Subject: Re: [Haskell-beginners] wxHaskell install errors Is your wx-config working ? You can try:??wx-config -help? If not, try with another, you can use these ones: - ? download from https://sites.google.com/site/wxconfig/sourcecode ? ? and compile with?g++ wx-config.cpp -o wx-config.exe - ? or download directly the .exe from ??http://sourceforge.net/projects/wxhaskell/files/wx-config-win/ ? ?? Regards, Carlos Gomez -- Message: 3 Date: Wed, 6 Jun 2012 11:52:03 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] wxHaskell install errors To: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01a2767cb...@mail.cs.mum.edu
Beginners Digest, Vol 48, Issue 11
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wxHaskell install errors (Gregory Guthrie) 2. Re: flatten comma operator (Brandon Allbery) 3. Re: wxHaskell path (Miguel Negrao) 4. Re: wxHaskell path (Henry Lockyer) 5. Re: wxHaskell install errors (carlos gomez) -- Message: 1 Date: Wed, 6 Jun 2012 15:15:20 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] wxHaskell install errors To: carlos gomez carliro...@gmail.com Cc: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01a2767cb...@mail.cs.mum.edu Content-Type: text/plain; charset=us-ascii First, you should make sure for yourself that wxWidgets 2.9 is well installed, for that you can try to build the wxwidgets' examples cd c:\wx\samples\minimal mingw32-make -f makefile.gcc BUILD=debug Thanks, good test, it fails. /e/plang/libraries/wxWidgets2.9/samples/minimal $ mingw32-make -f makefile.gcc BUILD=debug if not exist gcc_mswuddll mkdir gcc_mswuddll windres --use-temp-file -i../../samples/sample.rc -ogcc_mswuddll\minimal_sample_rc.o--define __WXMSW__ --define _UNICODE -- include-dir .\..\..\lib\gc c_dll\mswud --include-dir ./../../include --include-dir . --define WXUSINGDLL --include-dir ./../../samples --define NOPCH g++ -c -o gcc_mswuddll\minimal_minimal.o -g -O0 -mthreads -DHAVE_W32API_H -D__WXMSW__ -D_UNICODE -I.\..\..\lib\gcc_dll\mswud -I.\..\..\include -W -Wall -I. -DWXUSINGDLL -I.\..\..\samples -DNOPCH -Wno-ctor-dtor-privacy -MTgcc_mswuddll\minimal_minimal.o -MFgcc_mswuddll\minimal_minimal.o.d -MD -MP minimal.cpp In file included from .\..\..\include/wx/defs.h:28:0, from .\..\..\include/wx/wxprec.h:13, from minimal.cpp:21: .\..\..\include/wx/platform.h:181:22: fatal error: wx/setup.h: No such file or directory compilation terminated. mingw32-make: *** [gcc_mswuddll\minimal_minimal.o] Error 1 (I did have to start a mingw shell to do this, it won't run from a cmd line.) Not sure what to make of it... I still wish I could just get a binary to install like was available from wxPack for 2.8! :-) Then, I can think that it is just a problem of configuring and installing wxhaskell. For the paths you have to set, probably the wxc is not installed on your pc yet, and probably that's why you couldn't find. But you should follow the way setting those paths and put the right versions of the libraries you are installing. Yes, probably wxc is not installed, but that is the problem I am stuck at I think. -- Message: 2 Date: Wed, 6 Jun 2012 17:17:27 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] flatten comma operator To: Arlen Cuss a...@unnali.com Cc: beginners@haskell.org Message-ID: CAKFCL4U=g1_bSPPk=0qjw+g7oauwoc2nokor8bavokuagko...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Wed, Jun 6, 2012 at 7:06 AM, Arlen Cuss a...@unnali.com wrote: And as Brent pointed out also, it is. :) By the way, so is (,,,)! I suspect GHC allows any number. The Maybe not any number; more than 127 elements in a tuple used to cause core dumps -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120606/eb1313f2/attachment-0001.htm -- Message: 3 Date: Wed, 6 Jun 2012 22:18:49 +0100 From: Miguel Negrao miguel.negrao-li...@friendlyvirus.org Subject: Re: [Haskell-beginners] wxHaskell path To: beginners@haskell.org Message-ID: e5654eb9-0f84-46ac-8f59-99e795c19...@friendlyvirus.org Content-Type: text/plain; charset=windows-1252 Hi Henry, A 06/06/2012, ?s 12:31, Henry Lockyer escreveu: Thanks a lot Miguel. I recently discovered your posts about 'reactive banana' and wxHaskell and started looking through them. Unfortunately I am a c/c++ compilation/make/etc. and general unix newbie, or oldbie in my case, (amongst many other areas of deep ignorance
Beginners Digest, Vol 48, Issue 12
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wxHaskell install errors (Henry Lockyer) 2. Re: wxHaskell install errors (Gregory Guthrie) 3. Re: wxHaskell install errors (Gregory Guthrie) 4. Re: wxHaskell install errors (Gregory Guthrie) 5. Re: wxHaskell install errors (carlos gomez) 6. Re: wxHaskell install errors (Henry Lockyer) -- Message: 1 Date: Thu, 7 Jun 2012 01:55:25 +0100 From: Henry Lockyer henry.lock...@ntlworld.com Subject: Re: [Haskell-beginners] wxHaskell install errors To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org Message-ID: 576a8abf-8df6-4bb0-a876-140155821...@ntlworld.com Content-Type: text/plain; charset=us-ascii Hi Gregory, just been looking at your thread here (We seem to be having somewhat parallel problems - I am struggling with installing wxHAskell on mac osx). I was wondering, if you give the command wx-config --release What do you get ? If it says 2.8 (which is what I get) then presumably your 'path' is still pointing to the earlier version. And this would fit with Heinrich Apfelmus's comments ? I am struggling to make sense of path settings, and I raised some questions in another thread/s. In the wxHaskell installation instructions for wxWidgets 2.8 I saw this: We assume in this guide that the variable $wxwin points to your wxWidgets installation directory, for example: ~/dev/wxGTK-2.8.10. It is not in a windows specific part of the instructions, though I wonder (from the name) if it is just relevant for windows (though 'win' could also denote 'Widgets INstallation' perhaps). Do you recognise $wxwin (and what is it set to in your case?). I wonder if this may be implicated in the path settings for 2.9 too. I was also very interested by your If the libraries are already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where they are. I have not got to the cabal step yet (still trying to reach some confidence I have widgets installed and configured correctly!) but it seems this may be the (at least an) answer to the path aspect if all else fails with trying to get an auto default path working. Cheers/ Henry On 6 Jun 2012, at 21:15, Gregory Guthrie wrote: First, you should make sure for yourself that wxWidgets 2.9 is well installed, for that you can try to build the wxwidgets' examples cd c:\wx\samples\minimal mingw32-make -f makefile.gcc BUILD=debug Thanks, good test, it fails. /e/plang/libraries/wxWidgets2.9/samples/minimal $ mingw32-make -f makefile.gcc BUILD=debug if not exist gcc_mswuddll mkdir gcc_mswuddll windres --use-temp-file -i../../samples/sample.rc -ogcc_mswuddll\minimal_sample_rc.o--define __WXMSW__ --define _UNICODE -- include-dir .\..\..\lib\gc c_dll\mswud --include-dir ./../../include --include-dir . --define WXUSINGDLL --include-dir ./../../samples --define NOPCH g++ -c -o gcc_mswuddll\minimal_minimal.o -g -O0 -mthreads -DHAVE_W32API_H -D__WXMSW__ -D_UNICODE -I.\..\..\lib\gcc_dll\mswud -I.\..\..\include -W -Wall -I. -DWXUSINGDLL -I.\..\..\samples -DNOPCH -Wno-ctor-dtor-privacy -MTgcc_mswuddll\minimal_minimal.o -MFgcc_mswuddll\minimal_minimal.o.d -MD -MP minimal.cpp In file included from .\..\..\include/wx/defs.h:28:0, from .\..\..\include/wx/wxprec.h:13, from minimal.cpp:21: .\..\..\include/wx/platform.h:181:22: fatal error: wx/setup.h: No such file or directory compilation terminated. mingw32-make: *** [gcc_mswuddll\minimal_minimal.o] Error 1 (I did have to start a mingw shell to do this, it won't run from a cmd line.) Not sure what to make of it... I still wish I could just get a binary to install like was available from wxPack for 2.8! :-) Then, I can think that it is just a problem of configuring and installing wxhaskell. For the paths you have to set, probably the wxc is not installed on your pc yet, and probably that's why you couldn't find. But you should follow the way setting those paths and put the right versions of the libraries you are installing. Yes, probably wxc is not installed, but that is the problem I am stuck at I think. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part
Beginners Digest, Vol 48, Issue 13
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wxHaskell path (Henry Lockyer) -- Message: 1 Date: Thu, 7 Jun 2012 10:56:30 +0100 From: Henry Lockyer henry.lock...@ntlworld.com Subject: Re: [Haskell-beginners] wxHaskell path To: beginners@haskell.org Message-ID: 4c4be76f-6e35-4cf3-9c61-7944697d7...@ntlworld.com Content-Type: text/plain; charset=us-ascii Anyone know if/how $wxwin also needs to be set on macosx for wxHaskell 0.9 /wxWidgets 2.8 ? and/or wxHAskell 0.13 / wxWidgets 2.9 ? -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 48, Issue 13 *
Beginners Digest, Vol 48, Issue 14
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Strange difference in behaviour between ghc and ghci (Matthew Moppett) 2. Re: Strange difference in behaviour between ghc and ghci (Arlen Cuss) 3. Re: flatten comma operator (Arlen Cuss) 4. Re: Strange difference in behaviour between ghc and ghci (Andres L?h) 5. Re: Strange difference in behaviour between ghc and ghci (Henry Lockyer) 6. Re: Strange difference in behaviour between ghc and ghci (Henry Lockyer) 7. Re: Strange difference in behaviour between ghc and ghci (Matthew Moppett) -- Message: 1 Date: Thu, 7 Jun 2012 21:22:23 +1000 From: Matthew Moppett matthewmopp...@gmail.com Subject: [Haskell-beginners] Strange difference in behaviour between ghc and ghci To: beginners@haskell.org Message-ID: CAMLEjZAi7waUto4TaqegwJ1-4eBCT=ifcvjaylatpjuxkcp...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I have a very simple Haskell file (HelloWorld.hs) that reads like this: main = do putStr What's your name? n - getLine putStrLn $ Pleased to meet you, ++ n When I load it into ghci, I get the following result, as expected: [1 of 1] Compiling Main ( HelloWorld.hs, interpreted ) Ok, modules loaded: Main. *Main main What's your name? Matt Pleased to meet you, Matt *Main However, when I compile the same file using ghc and run it in a terminal, I get a very different result: matt@matt-Lenovo-G575:~/Haskell$ ghc HelloWorld.hs [1 of 1] Compiling Main ( HelloWorld.hs, HelloWorld.o ) Linking HelloWorld ... matt@matt-Lenovo-G575:~/Haskell$ ./HelloWorld Matt What's your name? Pleased to meet you, Matt matt@matt-Lenovo-G575:~/Haskell$ -- in other words, the getLine action is being run before the putStr action, for some strange reason. Is this a bug? Can anyone enlighten me as to what might be going on? Regards, Matt. -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120607/90f03058/attachment-0001.htm -- Message: 2 Date: Thu, 7 Jun 2012 21:28:53 +1000 From: Arlen Cuss a...@unnali.com Subject: Re: [Haskell-beginners] Strange difference in behaviour between ghc and ghci To: Matthew Moppett matthewmopp...@gmail.com Cc: beginners@haskell.org Message-ID: 525ca83d7d7c47888342df367da02...@unnali.com Content-Type: text/plain; charset=utf-8 Hello! See this similar mailing list question from 2006: http://www.haskell.org/pipermail/haskell/2006-September/018430.html The short answer is that GHCi buffers differently, so you need to be more explicit about flushing. HTH, Arlen On Thursday, 7 June 2012 at 9:22 PM, Matthew Moppett wrote: I have a very simple Haskell file (HelloWorld.hs) that reads like this: main = do putStr What's your name? n - getLine putStrLn $ Pleased to meet you, ++ n When I load it into ghci, I get the following result, as expected: [1 of 1] Compiling Main ( HelloWorld.hs, interpreted ) Ok, modules loaded: Main. *Main main What's your name? Matt Pleased to meet you, Matt *Main However, when I compile the same file using ghc and run it in a terminal, I get a very different result: matt@matt-Lenovo-G575:~/Haskell$ ghc HelloWorld.hs [1 of 1] Compiling Main ( HelloWorld.hs, HelloWorld.o ) Linking HelloWorld ... matt@matt-Lenovo-G575:~/Haskell$ ./HelloWorld Matt What's your name? Pleased to meet you, Matt matt@matt-Lenovo-G575:~/Haskell$ -- in other words, the getLine action is being run before the putStr action, for some strange reason. Is this a bug? Can anyone enlighten me as to what might be going on? Regards, Matt. ___ Beginners mailing list Beginners@haskell.org (mailto:Beginners@haskell.org) http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Thu, 7 Jun 2012 21:30:32 +1000 From: Arlen Cuss a...@unnali.com Subject: Re: [Haskell-beginners] flatten comma operator To: Brandon Allbery allber...@gmail.com Cc: beginners@haskell.org Message-ID: e6227490970f4be6a30ba0462f72c...@unnali.com Content-Type: text/plain; charset=utf-8 Hmm. I've tested over 6,432 to work, but I'm not sure this has any point any more ? ;-) On Thursday, 7 June 2012 at 7:17 AM, Brandon Allbery wrote: On Wed, Jun 6, 2012 at 7:06 AM, Arlen Cuss
Beginners Digest, Vol 48, Issue 15
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wrapping text in a multiline string (Rico Moorman) 2. Re: wxHaskell path (Heinrich Apfelmus) 3. Re: reactiva-banana : how to implement a certain type of throttling (Heinrich Apfelmus) 4. Re: wxHaskell path (Henry Lockyer) 5. Re: wxHaskell path (Henry Lockyer) 6. Re: wrapping text in a multiline string (Chadda? Fouch?) 7. Re: wxHaskell install errors (Gregory Guthrie) -- Message: 1 Date: Thu, 7 Jun 2012 14:44:11 +0200 From: Rico Moorman rico.moor...@gmail.com Subject: Re: [Haskell-beginners] wrapping text in a multiline string To: Chadda? Fouch? chaddai.fou...@gmail.com Cc: beginners@haskell.org Message-ID: CAJrzcX1w0JQ4AO95J=urfkai6ko00hpnegjgu_lkdf_mkmw...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 What's non-obvious and trip a lot of people when they try to use regexes in Haskell is that most regex libraries use the same interface, which is specified in the regex-base and consists of several typeclasses that offers a very high degree of flexibility. =~and =~~ are only the simplified front-ends to this and are pretty inadequate for advanced usages (for instance compile and use multiple time the same regex, you should really avoid =~ in this case, or additional regex compilation options). To see the basic interface, look at Text.Regex.Base.RegexLike : http://hackage.haskell.org/packages/archive/regex-base/latest/doc/html/Text-Regex-Base-RegexLike.html . In particular, what you want to do should be done with makeRegexOpts and match (or matchM), note that the available compilation and execution options can vary depending on the regex library you use and for regex-pcre, they're documented there : http://hackage.haskell.org/packages/archive/regex-pcre/latest/doc/html/Text-Regex-PCRE-Wrap.html#g:4 -- Jeda? By the way, do you know other good resources on Regular expressions in Haskell and especially the multiple backends (tdfa, posix and pcre e.g.) in combination with the basic interface and how to use this all together? Some example code would be really useful. Furthermore the following page states that the Text.Regex.Base stuff is being exported again by the newer/other regex modules. http://hackage.haskell.org/packages/archive/regex-base/0.93.2/doc/html/Text-Regex-Base-Context.html Does this mean I should use the specific regex modules directly or should I import the base and then specific functionality from the engine modules? Thank you very much in advance, Best regards, Rico -- Message: 2 Date: Thu, 07 Jun 2012 14:44:35 +0200 From: Heinrich Apfelmus apfel...@quantentunnel.de Subject: Re: [Haskell-beginners] wxHaskell path To: beginners@haskell.org Message-ID: jqq7nj$2if$1...@dough.gmane.org Content-Type: text/plain; charset=UTF-8; format=flowed Henry Lockyer wrote: Anyone know if/how $wxwin also needs to be set on macosx for wxHaskell 0.9 /wxWidgets 2.8 ? and/or wxHAskell 0.13 / wxWidgets 2.9 ? I don't think it's needed. Installation instruction found on the internet are not always accurate. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com -- Message: 3 Date: Thu, 07 Jun 2012 15:52:07 +0200 From: Heinrich Apfelmus apfel...@quantentunnel.de Subject: Re: [Haskell-beginners] reactiva-banana : how to implement a certain type of throttling To: beginners@haskell.org Message-ID: jqqbm7$5tv$1...@dough.gmane.org Content-Type: text/plain; charset=UTF-8; format=flowed Miguel Negrao wrote: A 04/06/2012, ?s 16:11, Heinrich Apfelmus escreveu: Miguel, could you repost this question on Stackoverflow, so I can answer it there? I?ve reposted the question here: [..] Thanks! Ok, looking at Wave.hs I can see what I need to do to be able to delay an event by a certain amount of seconds. The scheduleQueue function there doesn?t exactly do what I need it to do, because it schedules relative to the last scheduled event. Essentially I would need to alter it such that the scheduling is done in absolute terms, so If I ask something to happen 5 seconds from now it should really happen 5 seconds from now instead of 5 seconds from the last event in queue. One way to do it would be to keep the scheduled times in UTC or some other time format and every time an event comes into the queue stop the timer, sort the event queue by the absolute times, check how long is
Beginners Digest, Vol 48, Issue 16
Send Beginners mailing list submissions to
beginners@haskell.org
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http://www.haskell.org/mailman/listinfo/beginners
or, via email, send a message with subject or body 'help' to
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than Re: Contents of Beginners digest...
Today's Topics:
1. Scoping within arrow notation (using HXT)? (Michael Alan Dorman)
2. Re: Scoping within arrow notation (using HXT)?
(Ertugrul S?ylemez)
--
Message: 1
Date: Fri, 08 Jun 2012 11:48:23 -0400
From: Michael Alan Dorman mdor...@ironicdesign.com
Subject: [Haskell-beginners] Scoping within arrow notation (using
HXT)?
To: beginners@haskell.org
Message-ID: 87vcj1vm7s@ironicdesign.com
Content-Type: text/plain
Hey, Haskellers,
I'm trying to use state threaded through an arrow in some HXT code to
avoid passing explicit parameters through several layers of functions,
but I think I'm not understanding quite what the arrow notation is
doing, because when I try to use a value I'm extracting from the state,
I'm getting a scope error.
I had many ways I was prepared for the code to be wrong, but that one
has me baffled. Any suggestions?
Mike.
{-# LANGUAGE Arrows, NoMonomorphismRestriction #-}
module HXTTest () where
import Text.XML.HXT.Core
data Info = Info {
value :: String
} deriving (Show)
info = Info { value = foo }
html = htmlhead/headbodydiv class='foo'llama/div/body;
-- print (runSLA (getState arr value) info html)
-- Div class is static, no reference to state
findFoo =
proc content - do
(deep (isElem
hasName div
hasAttrValue class (== foo))) - content
-- print (runSLA (hread findFoo) info html)
-- Extract class from state, but don't use it
findFoo' =
proc content - do
divName - (getState arr value) - content
content - (deep (isElem
hasName div
hasAttrValue class (== foo)))
-- print (runSLA (hread findFoo') info html)
-- Extract class from state, try to use it: Not in scope: `divName'
-- findFoo'' =
-- proc content - do
-- divName - (getState arr value) - content
-- content - (deep (isElem
-- hasName div
-- hasAttrValue class (== divName)))
--
Message: 2
Date: Fri, 8 Jun 2012 18:20:13 +0200
From: Ertugrul S?ylemez e...@ertes.de
Subject: Re: [Haskell-beginners] Scoping within arrow notation (using
HXT)?
To: beginners@haskell.org
Message-ID: 20120608182013.5ffd1...@angst.streitmacht.eu
Content-Type: text/plain; charset=us-ascii
Hello there,
the structure of an arrow computation cannot depend on inputs. All
arrow variables (to the left of '-' or '-') are inputs to following
computations. For instance:
proc x1 - do
x2 - c1 - x1
x3 - c2 - x2
returnA - f x2 x3
The variables x1, x2 and x3 are arrow variables and are out of scope
to the left of '-', because if they were in scope, the structure of the
computation could depend on arrow variables, and you would in fact have
a monad instead of an arrow.
Note also that 'proc x - c - x' is the same as 'c', and 'do' notation
is an extension to 'proc' notation.
You may be interested in my (unfinished) arrow tutorial:
http://ertes.de/new/tutorials/arrows.html
Greets,
Ertugrul
Michael Alan Dorman mdor...@ironicdesign.com wrote:
I'm trying to use state threaded through an arrow in some HXT code to
avoid passing explicit parameters through several layers of functions,
but I think I'm not understanding quite what the arrow notation is
doing, because when I try to use a value I'm extracting from the
state, I'm getting a scope error.
--
nightmare = unsafePerformIO (getWrongWife = sex)
http://ertes.de/
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*
Beginners Digest, Vol 48, Issue 17
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: wrapping text in a multiline string (Chadda? Fouch?) 2. Re: wrapping text in a multiline string (Chadda? Fouch?) -- Message: 1 Date: Sun, 10 Jun 2012 14:04:35 +0200 From: Chadda? Fouch? chaddai.fou...@gmail.com Subject: Re: [Haskell-beginners] wrapping text in a multiline string To: Rico Moorman rico.moor...@gmail.com Cc: beginners beginners@haskell.org Message-ID: CANfjZRav-xdWgZ-4vfJG5S-21b=-vy_cgZjXCk1Jeum5mv=z=a...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Fri, Jun 8, 2012 at 1:33 PM, Rico Moorman rico.moor...@gmail.com wrote: Or you could just use matchM : ? ? ? ?go text = case RE.matchM regex' text of ? ? ? ? ? Just (before, match, after) - ? ? ? ? ? ? ? before ++ replace' match ++ go after ? ? ? ? ? _ - text and have match be a string, just like before (since you don't use all the power of MatchText anyway). Thank you very much for this suggestion. It works correctly. This is the final function (for reference): regexReplace :: String - (String - String) - String - String regexReplace pattern replace text = go text ? ?where ? ? ? ?regex = RE.makeRegexOpts compOpts RE.defaultExecOpt pattern ? ? ? ?compOpts = RE.compMultiline + RE.compDotAll ? ? ? ?go text = case RE.matchM regex text of ? ? ? ? ? ?Just (before, match, after) - ? ? ? ? ? ? ? ?before ++ replace match ++ go after ? ? ? ? ? ?_ - text It is really interesting that the result of a function can behave like this though. I mean that a different structure is returned based on the type (inferred/given) within the dependant function, e.g. [String] or Bool ... This is something that's possible with typeclass in Haskell and one of the way they differ from interfaces in the OO world. The classic example is the Read typeclass and read :: (Read a) = String - a. One other thing I saw is that there can be a runtime error using the option compUTF8 even if the compNoUTF8Check is set too. I get: user error (Text.Regex.PCRE.String died: (ReturnCode (-10),Error in Text.Regex.PCRE.Wrap: ReturnCode (-10))) which is the error code for bad utf8 (PCRE_ERROR_BADUTF8) according to http://www.pcre.org/pcre.txt . Luckily I don't seem to need those options (yet). Would there be some way to catch/trace/fix those error somehow? Fix I don't know since that's an internal error of the PCRE package or library but you can catch exceptions though only in the IO monad. In this particular case there may be an alternative since what fails is the compilation of the regex itself and makeRegexOpts has an alternative which handle errors : makeRegexOptsM . In this case writing your whole replace function in the Maybe monad would probably be a good idea : regexMaybeReplace :: String - (String - String) - String - Maybe String regexMaybeReplace pattern replace text = do let compOpts = RE.compMultiline + RE.compDotAll regex - RE.makeRegexOpts compOpts RE.defaultExecOpt pattern (before, match, after) - RE.matchM regex text return $ before ++ replace match ++ regexReplace after regexReplace :: String - (String - String) - String - String regexReplace pattern replace text = fromMaybe text (regexMaybeReplace pattern replace text) Or something like that. -- Jeda? -- Message: 2 Date: Sun, 10 Jun 2012 14:05:45 +0200 From: Chadda? Fouch? chaddai.fou...@gmail.com Subject: Re: [Haskell-beginners] wrapping text in a multiline string To: Rico Moorman rico.moor...@gmail.com Cc: beginners beginners@haskell.org Message-ID: CANfjZRZj2u5K=hs0gstwthbz4ychnrwguut9ix1xofj1zed...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Sun, Jun 10, 2012 at 2:04 PM, Chadda? Fouch? chaddai.fou...@gmail.com wrote: regexMaybeReplace :: String - (String - String) - String - Maybe String regexMaybeReplace pattern replace text = do ? let compOpts = RE.compMultiline + RE.compDotAll ? regex - RE.makeRegexOpts compOpts RE.defaultExecOpt pattern Oops, of course I meant : regex - RE.makeRegexOptsM compOpts RE.defaultExecOpt pattern -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 48, Issue 17 *
Beginners Digest, Vol 48, Issue 18
Send Beginners mailing list submissions to
beginners@haskell.org
To subscribe or unsubscribe via the World Wide Web, visit
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or, via email, send a message with subject or body 'help' to
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You can reach the person managing the list at
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When replying, please edit your Subject line so it is more specific
than Re: Contents of Beginners digest...
Today's Topics:
1. HXT and missing or null values (Ian Knopke)
2. cabal trouble(s!) (Gregory Guthrie)
--
Message: 1
Date: Wed, 13 Jun 2012 16:29:32 +0100
From: Ian Knopke ian.kno...@gmail.com
Subject: [Haskell-beginners] HXT and missing or null values
To: beginners-requ...@haskell.org, beginners@haskell.org
Message-ID:
CAC+f4wkJQMYp-N==pp8c3yhinj22yy-znzb1hc-ddamh4fj...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
I have an xml file I'm trying to parse using HXT. This is the code
(for some reason the list seems to be rejecting the XML example):
data Thing = Thing {first :: String, second :: String}
getThings = atTag thing
proc x - do
first - text atTag first - x
second - text atTag second - x
returnA - Thing {first = first,second = second}
atTag tag = deep (isElem hasName tag)
text = getChildren getText
parseThings str = runX (readString [withValidate no] str getThings)
The problem is that sometimes one of the tags is empty.
I'd like the code to return something like Thing
{first=val,second=} but instead the entire entry is skipped. Can
someone explain to me what I need to do to get a null or empty string
value inserted instead?
Ian
--
Message: 2
Date: Wed, 13 Jun 2012 12:23:05 -0500
From: Gregory Guthrie guth...@mum.edu
Subject: [Haskell-beginners] cabal trouble(s!)
To: beginners@haskell.org beginners@haskell.org
Message-ID:
08ef9da445c4b5439c4733e1f35705ba01a2767cb...@mail.cs.mum.edu
Content-Type: text/plain; charset=us-ascii
I have lots of problems with cabal - not sure why or how to correct them.
ghc-pkg check reports tons of issues, but all seem to be haddock-html, which
doesn't sound too serious, or haddock-interfaces.
Warning: haddock-html:
C:\Users\guthrie\AppData\Roaming\cabal\doc\wxdirect-0.90.0.1\html doesn't exist
or isn't a directory
...
Cabal install errors, For example;
C:\Users\guthriecabal install gloss-examples
Resolving dependencies...
Configuring gloss-raster-1.7.4.4...
Building gloss-raster-1.7.4.4...
Preprocessing library gloss-raster-1.7.4.4...
[1 of 2] Compiling Graphics.Gloss.Raster.Array (
Graphics\Gloss\Raster\Array.hs, dist\build\Graphics\Gloss\Raster\Array.o )
Warning: Couldn't figure out LLVM version!
Make sure you have installed LLVM
ghc.exe: could not execute: opt
What is LLVM, and do/how I need to install it?
and another (of many) - perhaps unrelated:
C:\Users\guthrie\AppData\Roaming\cabal\bincabal install wxc
Resolving dependencies...
command line: cannot satisfy -package Cabal-1.10.2.0:
Cabal-1.10.2.0-db589dd5d526d3111ac2fde0f9ab986c is unusable due to missing
or recursive dependencies:
array-0.3.0.2-8e9cd0144e87fa9cc86cc9031631c4f3 base-4.3.1.0-f520cd232cc386
346843c4a12b63f44b containers-0.4.0.0-18deac99a132f04751d862b77aab136e
directory
-1.1.0.0-3a2367d72569467a8af8a231656ff1b8
filepath-1.2.0.0-f132e9f7703da4e20a47f
f2b9acf1ea1 old-time-1.0.0.6-445ce39cbcebd38069c25c0f383b728d
pretty-1.0.1.2-abc
7c632374e50e1c1927987c2651f0f
process-1.0.1.5-b3dded8e54a2e13d22af410bdcfafff4
(use -v for more information)
cabal: Error: some packages failed to install:
wxc-0.90.0.3 failed during the configure step. The exception was:
ExitFailure 1
Trying to resolve them:
C:\Users\guthrie\AppData\Roaming\cabal\bincabal install base
Resolving dependencies...
cabal: internal error: impossible
I've had several others, not sure if they are package specific issues, or some
larger issue with cabal and libraries.
So I tried to fix them from a suggestion in SO; delete the ~/ghc ~/cabal
files and restart cabal, by a cabal install cabal-install.
It gives:
C:\Users\guthriecabal install cabal-install
Resolving dependencies...
In order, the following would be installed:
deepseq-1.3.0.0 (reinstall) changes: array-0.4.0.0 - 0.3.0.3
containers-0.4.2.1 (reinstall) changes: array-0.4.0.0 - 0.3.0.3
old-time-1.0.0.7 (new version)
directory-1.1.0.2 (reinstall) changes: filepath-1.3.0.0 - 1.2.0.1,
old-time-1.1.0.0 - 1.0.0.7
...
cabal: The following packages are likely to be broken by the reinstalls:
time-1.4
wxdirect-0.90.0.1
random-1.0.1.1
haskell-platform-2012.2.0.0
QuickCheck-2.4.2
...
ghc-7.4.1
...
Cabal-1.14.0
process-1.1.0.1
haskell98-1.1.0.1
haskell-src-1.0.1.4
Beginners Digest, Vol 48, Issue 19
Send Beginners mailing list submissions to
beginners@haskell.org
To subscribe or unsubscribe via the World Wide Web, visit
http://www.haskell.org/mailman/listinfo/beginners
or, via email, send a message with subject or body 'help' to
beginners-requ...@haskell.org
You can reach the person managing the list at
beginners-ow...@haskell.org
When replying, please edit your Subject line so it is more specific
than Re: Contents of Beginners digest...
Today's Topics:
1. HXT and missing or null values (Ian Knopke)
2. Difference between Char and Data.Char modules (Ken Overton)
3. Re: Difference between Char and Data.Charmodules
(Stephen Tetley)
4. Re: Difference between Char and Data.Charmodules (Brent Yorgey)
5. Re: Difference between Char and Data.Char modules (Ken Overton)
6. Re: Difference between Char and Data.Charmodules
(Stephen Tetley)
7. the download package fail to install (Song Zhang)
--
Message: 1
Date: Thu, 14 Jun 2012 17:37:06 +0100
From: Ian Knopke ian.kno...@gmail.com
Subject: [Haskell-beginners] HXT and missing or null values
To: beginners@haskell.org
Message-ID:
CAC+f4w=atir2atjwxbwgzjidr3ituxev1suykgmwnwpf2ss...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
I got it. For anyone else running into the problem from my earlier
email, the way to get a null string is as follows:
Replace this line:
second - text atTag second - x
with this:
second - ((text `orElse` (constA )) atTag second - x
Fixed program:
data Thing = Thing {first :: String, second :: String}
getThings = atTag thing
proc x - do
first - text atTag first - x
second - ((text `orElse` (constA )) atTag second - x
returnA - Thing {first = first,second = second}
atTag tag = deep (isElem hasName tag)
text = getChildren getText
parseThings str = runX (readString [withValidate no] str getThings)
--
Message: 2
Date: Thu, 14 Jun 2012 19:05:58 +
From: Ken Overton kover...@lab49.com
Subject: [Haskell-beginners] Difference between Char and Data.Char
modules
To: 'beginners@haskell.org' beginners@haskell.org
Message-ID:
b6368fed4eebe24fac9de115cf5c8c66afe...@exchange04b.lab49.com
Content-Type: text/plain; charset=utf-8
I just started looking at the Happy packag; I get a compile error when
attempting to build examples/glr/expr-eval:
ExprData.hs:9:8:
Could not find module `Char'
It is a member of the hidden package `haskell98-2.0.0.1'.
ExprData.hs:9 says ?import Char? and if I change this to ?import Data.Char? it
compiles correctly (then I get a similar message for System, but when I
understand Char I expect I will understand this too).
Could someone kindly explain the difference between these two modules? From the
look of the error, I?m guessing there?s a history lesson involved?
Thanks,
Ken
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Message: 3
Date: Thu, 14 Jun 2012 20:27:11 +0100
From: Stephen Tetley stephen.tet...@gmail.com
Subject: Re: [Haskell-beginners] Difference between Char and Data.Char
modules
To: Ken Overton kover...@lab49.com
Cc: beginners@haskell.org beginners@haskell.org
Message-ID:
CAB2TPRBB7du-obYwOghjuc=bgczicmtblfxtgec-p-11ksx...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
Char dates from the Haskell 98 specification, before hierarchical
modules were standardised. Data.Char is the newer hierarchical module
- it has been the de facto standard for a long time. Haskell 98 is
still supported by GHC but it is no longer the default - I think you
have to provide flags at the command line to get H98 automatically.
I'm not sure if the GLR (or attribute grammar) bits of Happy are
actively used, so you might expect a few infelicities if you try to
use them.
--
Message: 4
Date: Thu, 14 Jun 2012 15:32:39 -0400
From: Brent Yorgey byor...@seas.upenn.edu
Subject: Re:
Beginners Digest, Vol 48, Issue 20
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: the download package fail to install (Henk-Jan van Tuyl) -- Message: 1 Date: Fri, 15 Jun 2012 23:30:32 +0200 From: Henk-Jan van Tuyl hjgt...@chello.nl Subject: Re: [Haskell-beginners] the download package fail to install To: beginners@haskell.org, Song Zhang vxan...@gmail.com Message-ID: op.wfyrc6anpz0...@zen5.arnhem.chello.nl Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes On Fri, 15 Jun 2012 07:53:32 +0200, Song Zhang vxan...@gmail.com wrote: Hi There is a package for High-level file download based on URLs called download, but failed to build on windows, If you don't know it, you can refer to hackage first. I compiled in C, but did not get useful massage, anyone can help me a little to fix that. cabal install download get a bad header file If you give the following command, you have the source code on disk cabal unpack download Try to install, with debug messages: cd download-0.3.2 cabal install -v3 Near the end, you will see: cbits/download.h:49:15: error: 'MAXHOSTNAMELEN' undeclared here (not in a function) cbits/download.h uses the macro MAXHOSTNAMELEN; on a Windows system, this is defined in a different header file, A simple solution is inserting the following lines after line 44 in download.h: #ifdef _WIN32 #define MAXHOSTNAMELEN 256 #endif This results in a complaint about macro FILE not being defined; this can be solved by adding line: #include stddef.h The error message now is: In file included from C:\DOCUME~1\Henk-Jan\LOCALS~1\Temp\1848.c:1:0: cbits/download.h:98:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'FILE' I hope someone else will solve this last(?) problem. Regards, Henk-Jan van Tuyl -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming -- -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 48, Issue 20 *
Beginners Digest, Vol 48, Issue 21
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. about kind of (-) (Song Zhang) 2. Re: about kind of (-) (Ertugrul S?ylemez) 3. IO - getContents - putStrLn (Robert Heum?ller) 4. Re: IO - getContents - putStrLn (Tobias Brandt) 5. Re: IO - getContents - putStrLn (Michael Orlitzky) 6. Re: IO - getContents - putStrLn (Brandon Allbery) 7. Simplify (normalize) symbolic polynom-like expression (Daniel Hlynskyi) 8. Re: Simplify (normalize) symbolic polynom-like expression (M?t? Kov?cs) 9. problem with type (miro) -- Message: 1 Date: Sat, 16 Jun 2012 22:25:08 +0800 From: Song Zhang vxan...@gmail.com Subject: [Haskell-beginners] about kind of (-) To: beginners@haskell.org Message-ID: CACGMEOk6Xcn8J+4KhU1fKh=qyu8t-kebp0j7fo-0x-n9t-l...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 a function has also a kind. According to haskell report 2010 4.1.2 it is * - * - *, which is easy to understand. However in ghci I type :k (-). the output is ?? - ? - *. I want to know what do ?? and ? mean. Thanks -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120616/ab48d400/attachment-0001.htm -- Message: 2 Date: Sat, 16 Jun 2012 16:43:10 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] about kind of (-) To: beginners@haskell.org Message-ID: 20120616164310.1b177...@tritium.streitmacht.eu Content-Type: text/plain; charset=us-ascii Song Zhang vxan...@gmail.com wrote: a function has also a kind. According to haskell report 2010 4.1.2 it is * - * - *, which is easy to understand. However in ghci I type :k (-). the output is ?? - ? - *. I want to know what do ?? and ? mean. Thanks This has to do with primitive types like Int#. It basically says that the input type can be a primitive type, and if it is, then the output type must also be primitive. In fact since GHC 7.4 (or perhaps earlier) the kind is * - * - * as expected. Greets, Ertugrul -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120616/8f2973a5/attachment-0001.pgp -- Message: 3 Date: Sat, 16 Jun 2012 20:03:36 +0200 From: Robert Heum?ller mail...@heum.de Subject: [Haskell-beginners] IO - getContents - putStrLn To: beginners@haskell.org Message-ID: 20120616200336.7bd388cd@thor Content-Type: text/plain; charset=US-ASCII Hi, this is probably an easy question, but i simply can't figure out, why this does not work: import Data.Char main = do contents - getContents putStrLn $ show $ splitcomma contents splitcomma = split ',' split :: Char - String - [String] split _ = [] split sp (c:cs) | c == sp = : rest | otherwise = (c : head rest) : tail rest where rest = split sp cs The program compiles and runs without any problems. But there is absolutely no output, when f.eg. i type hello, world and hit return. Why would that be? Thank you very much -- Message: 4 Date: Sat, 16 Jun 2012 20:10:01 +0200 From: Tobias Brandt tob.bra...@googlemail.com Subject: Re: [Haskell-beginners] IO - getContents - putStrLn To: Robert Heum?ller mail...@heum.de Cc: beginners@haskell.org Message-ID: caoowqir7cubjgtwmcixpf9lrm6hrb6zb0gbgivebtt-esqi...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 On 16 June 2012 20:03, Robert Heum?ller mail...@heum.de wrote: The program compiles and runs without any problems. But there is absolutely no output, when f.eg. i type hello, world and hit return. Why would that be? getContents reads the entire input to the program. Under Linux you can terminate input with Ctrl-D. If you want to only read a single line, use getLine. -- Message: 5 Date: Sat, 16 Jun 2012 14:10:55 -0400 From: Michael Orlitzky mich...@orlitzky.com Subject: Re: [Haskell-beginners] IO - getContents - putStrLn To: beginners@haskell.org Message-ID: 4fdccc2f.4090...@orlitzky.com Content-Type: text/plain; charset=ISO-8859-1 On 06/16/12 14:03, Robert Heum?ller wrote: Hi, this is probably an easy question, but i simply can't figure out, why this does not work: ... The program compiles and runs without any problems. But
Beginners Digest, Vol 48, Issue 23
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: lambda notation vs function-argument notation in GHCi (Ozgur Akgun) 2. Re: lambda notation vs function-argument notation in GHCi (Morel Pisum) 3. how monomorphism restriction effects eta reduction (Song Zhang) 4. Re: problem with type (miro) -- Message: 1 Date: Sun, 17 Jun 2012 11:28:26 +0100 From: Ozgur Akgun ozgurak...@gmail.com Subject: Re: [Haskell-beginners] lambda notation vs function-argument notation in GHCi To: Morel Pisum morel.pi...@googlemail.com Cc: beginners@haskell.org Message-ID: CALzazPB6uvufwkU4192-=dLOZDBRfpV62tjs3dhbh-SXecO=q...@mail.gmail.com Content-Type: text/plain; charset=utf-8 http://www.haskell.org/haskellwiki/Monomorphism_restriction On 17 June 2012 08:13, Morel Pisum morel.pi...@googlemail.com wrote: Let's define a function in GHCi: Prelude let f s n = and (map (==s) n) Prelude :t f f :: Eq a = a - [a] - Bool This is fine. But when I define this function using lambda notation, I get this Prelude let f = \s n - and (map (==s) n) Prelude :t f f :: () - [()] - Bool which is really weird. Why does this happen? ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Ozgur Akgun -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120617/ec5d2b65/attachment-0001.htm -- Message: 2 Date: Sun, 17 Jun 2012 12:37:22 +0200 From: Morel Pisum morel.pi...@googlemail.com Subject: Re: [Haskell-beginners] lambda notation vs function-argument notation in GHCi To: Ozgur Akgun ozgurak...@gmail.com Cc: beginners@haskell.org Message-ID: 4fddb362.9000...@googlemail.com Content-Type: text/plain; charset=UTF-8 Ah, of course! I didn't think I will ever stumble upon this? Thank you! http://www.haskell.org/haskellwiki/Monomorphism_restriction On 17 June 2012 08:13, Morel Pisum morel.pi...@googlemail.com wrote: Let's define a function in GHCi: Prelude let f s n = and (map (==s) n) Prelude :t f f :: Eq a = a - [a] - Bool This is fine. But when I define this function using lambda notation, I get this Prelude let f = \s n - and (map (==s) n) Prelude :t f f :: () - [()] - Bool which is really weird. Why does this happen? -- Message: 3 Date: Mon, 18 Jun 2012 00:22:40 +0800 From: Song Zhang vxan...@gmail.com Subject: [Haskell-beginners] how monomorphism restriction effects eta reduction To: beginners@haskell.org Message-ID: cacgmeonsqaagoaaztaij7fhkhcrvpykttw8k5fsjfa8k9m5...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I think monomorphism restriction is for shared evaluation.like following function f xs = let len = genericLength xs in (len, len) from haskell wiki under monomorphism the type is Num t = [b] - (t, t), if it no monomorphism restriction the type will be (Num t, Num t1) = [b] - (t, t1) which lead to twice evaluation of len. However I didn't see how the restriction effects eta reduction, when define function like f = show, g = (==) or f = \x - show x, g = \x - \y - (x==y). anyone can explain it to me? Thanks a lot. -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120618/d507517c/attachment-0001.htm -- Message: 4 Date: Sun, 17 Jun 2012 20:53:35 +0200 From: miro miroslav.kar...@gmail.com Subject: Re: [Haskell-beginners] problem with type To: beginners@haskell.org Message-ID: 4fde27af.1020...@gmail.com Content-Type: text/plain; charset=iso-8859-1; Format=flowed Thank you! Miro On 6/17/12 9:08 AM, Morel Pisum wrote: What you want is probably checkNode :: String - [String] - Bool checkNode s nodes = and (map (==s) nodes) which returns True iff all nodes equal s. Am a bit stuck here,... please, what is wrong with this? checkNode :: String - [String] - Bool checkNode s nodes = [s == node | node- nodes ] src/me.hs:3:4: Couldn't match expected type `Bool' with actual type `[t0]' [1 of 1] Compiling Main ( src/me.hs, interpreted ) In the expression: [s == node | node- nodes] Failed, modules loaded: none. In an equation for `checkNode': checkNode s nodes = [s == node | node- nodes]
Beginners Digest, Vol 48, Issue 24
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Improving Performance (Robert Heum?ller) 2. Re: General Hints on Improving Performance - Example DBSCAN (Robert Heum?ller) 3. Re: Improving Performance (Ertugrul S?ylemez) 4. Re: Improving Performance (Robert Heum?ller) 5. Understanding how laziness works (Matt Ford) 6. Re: Improving Performance (Robert Heum?ller) 7. Re: Improving Performance (Ertugrul S?ylemez) 8. Re: Understanding how laziness works (Alexander Batischev) 9. Function application versus function composition performance (Matt Ford) -- Message: 1 Date: Tue, 19 Jun 2012 16:37:57 +0200 From: Robert Heum?ller mail...@heum.de Subject: [Haskell-beginners] Improving Performance To: beginners@haskell.org Message-ID: 20120619163757.1c528917@thor Content-Type: text/plain; charset=US-ASCII Hello, in order to tune my brain to functional thinking I've decided to start writing some real programs. After having spent a couple of days figuring out how to translate an imperative algorithm into stateless haskell I beleive I've now managed a simple implementation of the DBSCAN clustering algorithm. http://privatepaste.com/e6bb4fb665 This code has several drawbacks (and probably it doesn't work correctly after all) but I would like to tune its performance. Obviously the code calls several functions multiply with the same arguments. Haskell, being stateless should thus always yield the same resuts, correct? In this case performing the same calculations multiply seems pointless. My question: How would you go about improving this code? In any imperative language I would simply cache distances/neighborhoods in a matrix. Obviously this is not what the way to go in haskell? Thank you very much -- Message: 2 Date: Tue, 19 Jun 2012 16:45:51 +0200 From: Robert Heum?ller mail...@heum.de Subject: Re: [Haskell-beginners] General Hints on Improving Performance - Example DBSCAN To: beginners@haskell.org Message-ID: 20120619164551.5a2a337e@thor Content-Type: text/plain; charset=US-ASCII I'm sorry the Thread title is not very helpful... I hope this is better Hello, in order to tune my brain to functional thinking I've decided to start writing some real programs. After having spent a couple of days figuring out how to translate an imperative algorithm into stateless haskell I beleive I've now managed a simple implementation of the DBSCAN clustering algorithm. http://privatepaste.com/e6bb4fb665 This code has several drawbacks (and probably it doesn't work correctly after all) but I would like to tune its performance. Obviously the code calls several functions multiply with the same arguments. Haskell, being stateless should thus always yield the same resuts, correct? In this case performing the same calculations multiply seems pointless. My question: How would you go about improving this code? In any imperative language I would simply cache distances/neighborhoods in a matrix. Obviously this is not what the way to go in haskell? Thank you very much ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Tue, 19 Jun 2012 17:01:26 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] Improving Performance To: beginners@haskell.org Message-ID: 20120619170126.5c4b5...@tritium.streitmacht.eu Content-Type: text/plain; charset=utf-8 Robert Heum?ller mail...@heum.de wrote: in order to tune my brain to functional thinking I've decided to start writing some real programs. After having spent a couple of days figuring out how to translate an imperative algorithm into stateless haskell I beleive I've now managed a simple implementation of the DBSCAN clustering algorithm. http://privatepaste.com/e6bb4fb665 When asking people to review your code, it would be very helpful to write type signatures for your top-level functions. This alone makes code greatly more readable and also tells a lot about the quality right away. I advice you to get used to writing type signatures for yourself as well. Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. -- next part -- A non-text attachment was scrubbed... Name:
Beginners Digest, Vol 48, Issue 25
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Function application versus function composition performance (KC) 2. Re: Function application versus function composition performance (Ertugrul S?ylemez) -- Message: 1 Date: Tue, 19 Jun 2012 15:08:31 -0700 From: KC kc1...@gmail.com Subject: Re: [Haskell-beginners] Function application versus function composition performance To: Matt Ford m...@dancingfrog.co.uk, beginners@haskell.org, haskell-cafe haskell-c...@haskell.org Message-ID: camlkxymbnwy89vvofp6pec7g-pwtwsvc54veg5bnem3ytnr...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 A good functional programming language has a good code algebra after parsing to which algebraic transformations can be applied for optimization. For example, reducing the need for generating intermediate data structures. See: fusion. On Tue, Jun 19, 2012 at 3:01 PM, Matt Ford m...@dancingfrog.co.uk wrote: Hi All, My last question got me thinking (always dangerous): an expression that doubles a list and takes the 2nd element (index 1), I assume, goes through the following steps. double (double [1,2,3,4]) !! 1 double ( 1*2 : double [2,3,4]) !! 1 1*2*2 : double ( double [2,3,4] ) !! 1 1*2*2 : double ( 2*2 : double [3,4] ) !! 1 1*2*2 : 2*2*2 : double ( double [3,4] ) !! 1 2*2*2 8 Up until the element requested all the proceeding elements have to have the expression formed as Haskell process the calculation. Now, I want to compare this to using function composition ( double . double ) [ 1 ,2, 3, 4 ] !! 1 This is the bit I'm unsure of - what does the composition look like. It is easy to see that it could be simplified to something like: ( double . double) (x:xs) = x*4 : (double . double) xs This would mean the steps could be written (double . double) [ 1,2,3,4 ] !! 1 (1*4 : (double.double) [2,3,4]) !! 1 (1*4 : 2*4 : (double.double) [ 3,4 ]) !! 1 2*4 8 Ignoring the start and end steps, it will be half the number of steps compared to the application version. Significant then, over long lists. So is this true, are composite functions simplified in Haskell in general so that they may have improved performance over function application? I've seen posts on the internet that say it's a matter of style only: http://stackoverflow.com/questions/3030675/haskell-function-composition-and-function-application-idioms-correct-us . But my reasoning suggests it could be more than that. Perhaps, function application is similarly optimised - maybe by replacing all functions applications with composition and then simplifying? Or maybe the simplifying/optimisation step never happens? As you can see I'm just guessing at things :-) But it's nice to wonder. Many thanks for any pointers, Matt. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- -- Regards, KC -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120619/7c7dcd4d/attachment-0001.htm -- Message: 2 Date: Wed, 20 Jun 2012 01:10:03 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] Function application versus function composition performance To: beginners@haskell.org Message-ID: 20120620011003.2d5e3...@tritium.streitmacht.eu Content-Type: text/plain; charset=us-ascii Matt Ford m...@dancingfrog.co.uk wrote: So is this true, are composite functions simplified in Haskell in general so that they may have improved performance over function application? You may be forgetting that Haskell is lazily evaluated. If you have seen the output of compilers for strict languages like C you may find yourself somewhere between surprised and shocked to see what a Haskell compiler produces. The result is not a set of procedures, but a graph and the less nodes the higher the performance. To answer your question: A completely naive compiler will produce the most efficient code for function application. That's three nodes, one for the application node, one for the function, one for the argument. In that sense function application is in a sense an atom. In the case of applying two functions the result will be five nodes. On the other hand the function composition operator is compiled to what is called a supercombinator.
Beginners Digest, Vol 48, Issue 27
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: darcsden (Jack Henahan) 2. Re: darcsden (Rui Barreiro) -- Message: 1 Date: Mon, 25 Jun 2012 13:31:27 -0400 From: Jack Henahan jhena...@uvm.edu Subject: Re: [Haskell-beginners] darcsden To: Rui Barreiro rui.barre...@gmail.com Cc: beginners@haskell.org Message-ID: 52e42b77-0b6b-4482-80d7-4905a3b4d...@uvm.edu Content-Type: text/plain; charset=iso-8859-1 Do you get different results if you use `cabal install darcsden --solver=modular --avoid-reinstalls`? On Jun 21, 2012, at 6:51 PM, Rui Barreiro wrote: I would like to install darcsden on my machine, but I am having some difficulties. When I make cabal install I get this message: cabal: The following packages are likely to be broken by the reinstalls: bin-package-db-0.0.0.0 ghc-7.4.1 Use --force-reinstalls if you want to install anyway. what should I do? and why? Thanks ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 841 bytes Desc: Message signed with OpenPGP using GPGMail URL: http://www.haskell.org/pipermail/beginners/attachments/20120625/25aa0751/attachment-0001.pgp -- Message: 2 Date: Mon, 25 Jun 2012 23:21:47 +0100 From: Rui Barreiro rui.barre...@gmail.com Subject: Re: [Haskell-beginners] darcsden To: Jack Henahan jhena...@uvm.edu Cc: beginners@haskell.org Message-ID: ca+zr+nfn1worfuss5qboiffgdaeel-xmamjqlkp19iwae12...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I get the same error as with --force-reinstalls which is src/SSH/Crypto.hs:145:55: Not in scope: data constructor `RSA.PrivateKey' It seams to me that some code is based on an older version of Codec.Crypto.RSA. On Mon, Jun 25, 2012 at 6:31 PM, Jack Henahan jhena...@uvm.edu wrote: Do you get different results if you use `cabal install darcsden --solver=modular --avoid-reinstalls`? On Jun 21, 2012, at 6:51 PM, Rui Barreiro wrote: I would like to install darcsden on my machine, but I am having some difficulties. When I make cabal install I get this message: cabal: The following packages are likely to be broken by the reinstalls: bin-package-db-0.0.0.0 ghc-7.4.1 Use --force-reinstalls if you want to install anyway. what should I do? and why? Thanks ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120625/b4eee8dd/attachment-0001.htm -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 48, Issue 27 *
Beginners Digest, Vol 48, Issue 28
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. No accumulation of partially applied functions allowed? (Obscaenvs) 2. Re: No accumulation of partially applied functions allowed? (Brent Yorgey) 3. Re: No accumulation of partially applied functions allowed? (Jay Sulzberger) 4. Re: No accumulation of partially applied functions allowed? (Alec Story) 5. Re: No accumulation of partially applied functions allowed? (Jay Sulzberger) -- Message: 1 Date: Tue, 26 Jun 2012 22:08:49 +0200 From: Obscaenvs obscae...@gmail.com Subject: [Haskell-beginners] No accumulation of partially applied functions allowed? To: beginners@haskell.org Message-ID: 4fea16d1.3030...@gmail.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sorry if this is a less than stellar question. The problem: Given a function f :: a - a - a - b, make it work on a list instead: f `applyTo`[x,y,z] where [x,y,z] :: [a]. My stab at a general solution was ` applyTo f [] = error no arg applyTo f (x:xs) = go (f x) xs where go acc [] = acc go acc (y:[]) = acc y go acc (y:ys) = go (acc $ y) ys ` I thought this would work, functions being first class citizens but ghci complains: Occurs check: cannot construct the infinite type: t1 = t0 - t1 In the return type of a call of `acc' Probable cause: `acc' is applied to too many arguments In the expression: acc y In an equation for `go': go acc (y : []) = acc y The 'probable cause' isn't the real cause here, but something to do with the fact that it's impossible to accumulate functions in this way... Or am I just too tired too make it work? I can see that the type of `go` could be a problem, but is it insurmountable? /F -- Message: 2 Date: Tue, 26 Jun 2012 16:59:29 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] No accumulation of partially applied functions allowed? To: beginners@haskell.org Message-ID: 20120626205929.ga9...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Tue, Jun 26, 2012 at 10:08:49PM +0200, Obscaenvs wrote: Sorry if this is a less than stellar question. The problem: Given a function f :: a - a - a - b, make it work on a list instead: f `applyTo`[x,y,z] where [x,y,z] :: [a]. My stab at a general solution was ` applyTo f [] = error no arg applyTo f (x:xs) = go (f x) xs where go acc [] = acc go acc (y:[]) = acc y go acc (y:ys) = go (acc $ y) ys ` I thought this would work, functions being first class citizens but ghci complains: Occurs check: cannot construct the infinite type: t1 = t0 - t1 In the return type of a call of `acc' Probable cause: `acc' is applied to too many arguments In the expression: acc y In an equation for `go': go acc (y : []) = acc y The 'probable cause' isn't the real cause here, but something to do with the fact that it's impossible to accumulate functions in this way... Or am I just too tired too make it work? I can see that the type of `go` could be a problem, but is it insurmountable? The type of `go` is exactly the problem. In particular, the type of acc's first parameter. In the third clause of go's definition, we can see that `acc` and (acc $ y) are both used as the first argument to go, hence they must have the same type. However, this is impossible -- if acc has type (t0 - t1), then y must have type t0, and (acc $ y) has type t1, so it would have to be the case that t1 = t0 - t1 -- hence the error message. It is not possible in Haskell to define `applyTo`.* I know this function gets used a lot in lisp/scheme, but Haskell style is different. If you explain the context in which you wanted this function, perhaps we can help you figure out a better way to structure things so it is not needed. -Brent * At least not without crazy type class hackery. -- Message: 3 Date: Tue, 26 Jun 2012 17:19:28 -0400 (EDT) From: Jay Sulzberger j...@panix.com Subject: Re: [Haskell-beginners] No accumulation of partially applied functions allowed? To: beginners@haskell.org Message-ID: pine.neb.4.64.1206261705430.4...@panix3.panix.com Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed On Tue, 26 Jun 2012, Brent Yorgey byor...@seas.upenn.edu wrote: On Tue, Jun 26, 2012 at 10:08:49PM +0200, Obscaenvs wrote: Sorry if this is a
Beginners Digest, Vol 48, Issue 29
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: No accumulation of partially applied functions allowed? (ARJANEN Lo?c Jean David) 2. Re: No accumulation of partially applied functions allowed? (Brent Yorgey) -- Message: 1 Date: Wed, 27 Jun 2012 14:01:10 +0200 From: ARJANEN Lo?c Jean David arjanen.l...@gmail.com Subject: Re: [Haskell-beginners] No accumulation of partially applied functions allowed? To: beginners@haskell.org Message-ID: cab2q81ax8fy6xq5kvwweacq5ovdxj27ym+wrmbjgsh70g7-...@mail.gmail.com Content-Type: text/plain; charset=utf-8 It is easy, but inconvenient to define applyTo on tuples, which are Haskell's standard container for heterogeneous collections (that would basically be an extension of Prelude's uncurry), but they would be inconvenient to define and quite unwieldy to use. If you limit yourself to homogeneous collections (that is, lists), it's possible but using typeclass hackery and you shouldn't do so unless you need to. for an example of such techniques, see HaXRhttp://www.haskell.org/haskellwiki/HaXR or hs-json-rpc http://hackage.haskell.org/package/hs-json-rpc where this kind of tricks are used to implement remote calls. 2012/6/27 Jay Sulzberger: On Tue, 26 Jun 2012, Alec Story av...@cornell.edu wrote: Because of Haskell's type system, there are some expressions that you simply cannot compile. Most of them you don't *want* to compile because they do bad things (like add two strings, for example). Some things are legal in Lisp but don't typecheck in Haskell for exactly the reasons that Brent pointed out. They might make sense in some contexts, but the compiler isn't able to reason about them. Thanks, Alec. What is a formalized version of It is not possible in Haskell to define `applyTo`.* * At least not without crazy type class hackery. I think the difficulty must arise mainly from the *, meaning I think, any type in the above `applyTo`.*. Would it be easy/convenient to define `applyTo`.(a, b, c) where a is a type variable? In general can we, for any finite number n, where n 2, easily/conveniently define `applyTo`.(a1, a2, ..., an) ? Ah, I see that the problem is for lists of length 3, so for the type, if it be such, that I might write as [a, a, a], ah, OK, I will fire up GHCi and have a look. oo--JS. On Tue, Jun 26, 2012 at 5:19 PM, Jay Sulzberger j...@panix.com wrote: On Tue, 26 Jun 2012, Brent Yorgey byor...@seas.upenn.edu wrote: On Tue, Jun 26, 2012 at 10:08:49PM +0200, Obscaenvs wrote: Sorry if this is a less than stellar question. The problem: Given a function f :: a - a - a - b, make it work on a list instead: f `applyTo`[x,y,z] where [x,y,z] :: [a]. My stab at a general solution was ` applyTo f [] = error no arg applyTo f (x:xs) = go (f x) xs where go acc [] = acc go acc (y:[]) = acc y go acc (y:ys) = go (acc $ y) ys ` I thought this would work, functions being first class citizens but ghci complains: Occurs check: cannot construct the infinite type: t1 = t0 - t1 In the return type of a call of `acc' Probable cause: `acc' is applied to too many arguments In the expression: acc y In an equation for `go': go acc (y : []) = acc y The 'probable cause' isn't the real cause here, but something to do with the fact that it's impossible to accumulate functions in this way... Or am I just too tired too make it work? I can see that the type of `go` could be a problem, but is it insurmountable? The type of `go` is exactly the problem. In particular, the type of acc's first parameter. In the third clause of go's definition, we can see that `acc` and (acc $ y) are both used as the first argument to go, hence they must have the same type. However, this is impossible -- if acc has type (t0 - t1), then y must have type t0, and (acc $ y) has type t1, so it would have to be the case that t1 = t0 - t1 -- hence the error message. It is not possible in Haskell to define `applyTo`.* I know this function gets used a lot in lisp/scheme, but Haskell style is different. If you explain the context in which you wanted this function, perhaps we can help you figure out a better way to structure things so it is not needed. -Brent * At least not without crazy type class hackery. What is the difficulty? Is the difficulty at the level of syntax? Or is it that the type Haskell expression, perhaps Haskell form, to use an
Beginners Digest, Vol 48, Issue 30
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. test-framework (Mateusz Neumann) 2. Re: test-framework (Mateusz Neumann) 3. Help with Why Do Monads Matter blog post understanding (Matt Ford) -- Message: 1 Date: Fri, 29 Jun 2012 07:30:23 +0200 From: Mateusz Neumann mate...@neumanny.net Subject: [Haskell-beginners] test-framework To: beginners@haskell.org Message-ID: 20120629073023.03c72439@dragonfly.localdomain Content-Type: text/plain; charset=us-ascii Hi, I am currently writing testing routines for my project. I have came across an interesting test-framework (http://hackage.haskell.org/package/test-framework-0.6). Do you know it? I use QuickCheck2 provider (Test.Framework.Providers.QuickCheck2) to property tests. And here is my problem: I find configuring the provider very confusing, I cannot set (in Haskell code) for example number of tests to run or other QuickCheck parameters. Could you please help? Thanks -- Mateusz -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 230 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120629/5ff5a066/attachment-0001.pgp -- Message: 2 Date: Fri, 29 Jun 2012 09:58:34 +0200 From: Mateusz Neumann mate...@neumanny.net Subject: Re: [Haskell-beginners] test-framework To: Lorenzo Bolla lbo...@gmail.com, beginners@haskell.org Message-ID: 20120629095834.7208a123@dragonfly.localdomain Content-Type: text/plain; charset=us-ascii On Fri, 29 Jun 2012 08:43:33 +0100 Lorenzo Bolla lbo...@gmail.com wrote: Are the examples in the package distribution of any help? https://github.com/batterseapower/test-framework/blob/master/example/Test/Framework/Example.lhs L. I was thinking more about parametres set in Haskell code itself. There is something like TestOptions (http://hackage.haskell.org/packages/archive/test-framework/0.6/doc/html/Test-Framework-Options.html#t:TestOptions) and RunnerOptions (http://hackage.haskell.org/packages/archive/test-framework/0.6/doc/html/Test-Framework-Runners-Options.html) but I do not find any examples of using them. Similarly, I do not know how to set them up. On Fri, Jun 29, 2012 at 6:30 AM, Mateusz Neumann mate...@neumanny.netwrote: Hi, I am currently writing testing routines for my project. I have came across an interesting test-framework (http://hackage.haskell.org/package/test-framework-0.6). Do you know it? I use QuickCheck2 provider (Test.Framework.Providers.QuickCheck2) to property tests. And here is my problem: I find configuring the provider very confusing, I cannot set (in Haskell code) for example number of tests to run or other QuickCheck parameters. Could you please help? Thanks -- Mateusz ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Mateusz -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 230 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120629/07b87fea/attachment-0001.pgp -- Message: 3 Date: Fri, 29 Jun 2012 09:57:42 +0100 From: Matt Ford m...@dancingfrog.co.uk Subject: [Haskell-beginners] Help with Why Do Monads Matter blog post understanding To: beginners@haskell.org Message-ID: 20120629085741.gm20...@rss01.mhs.man.ac.uk Content-Type: text/plain; charset=utf-8 Hi, I've been reading the following blog post https://cdsmith.wordpress.com/2012/04/18/why-do-monads-matter/ And I think I like it. But there's a part that I don't get. For a set A, we will define the set Pref(A) to be the set of functions from application settings to the set A. Now watch closely: a function in context from A to B is just an ordinary function from A to Pref(B). In other words, you give it a value from the set A, and it gives you back another function that maps from application settings to the set B. This is in the functioning with dependency section and is talking about a procedure that uses outside info from preferences or application settings. If I set my prefs as follows configvar = 3 and define a function as follows add x = configvar + 6 So add?s signature is add: int - int What does prefs(int) look like? Is that even the
Beginners Digest, Vol 48, Issue 31
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Today's Topics:
1. FRP and a set of pairwise interacting(colliding) objects
(Nathan H?sken)
2. Re: FRP and a set of pairwise interacting(colliding)
objects (Ertugrul S?ylemez)
3. Re: test-framework (Michael Orlitzky)
4. Re: Help with Why Do Monads Matter blog post understanding
(Brent Yorgey)
5. Re: Help with Why Do Monads Matter blog post understanding
(Matt Ford)
6. Re: test-framework (Mateusz Neumann)
7. Re: Help with Why Do Monads Matter blog post understanding
(Paulo Pocinho)
8. Re: FRP and a set of pairwise interacting (colliding)
objects (Nathan H?sken)
--
Message: 1
Date: Fri, 29 Jun 2012 14:07:13 +0200
From: Nathan H?sken nathan.hues...@posteo.de
Subject: [Haskell-beginners] FRP and a set of pairwise interacting
(colliding) objects
To: beginners@haskell.org
Message-ID: 4fed9a71.2070...@posteo.de
Content-Type: text/plain; charset=ISO-8859-1
Hi,
I want to simulate as set of 2D objects, which can collide pairs wise
with each other.
In an OOP language, I would do this:
for (o1 in objects) {
for (o2 in objets) {
if (testCollision(o1, o2)) {
CollData cd = getCollisionData(o1,o2);
o1.reactToCollision(cd);
o2.reactToCollision(cd):
}
}
}
Now I want to do the same thing in Haskell with FRP.
Normally in FRP (correct me if I am wrong) I have for my objects a
Signal (or whatever it is called in the specific library), which gets as
input the collision events for this object (and probably more data, but
let's assume collision events are enough):
object :: Signal (Event CollData) ObjectState
The CollData events themself are generated at another place:
collisions :: Signal [ObjectState] (Event CollData)
But now the collisions are generated at one place, and processed at
another. This means that CollData must be somehow tagged to the objects
it belongs to (an ID for example). This again means that some function
must take the pool of all collision datas and distribute them to the
object Signals.
When I have a lot of objects, this means a significant overhead!
Now I am wondering if there is a nicer approach which avoids this overhead.
Thanks!
Nathan
--
Message: 2
Date: Fri, 29 Jun 2012 16:47:44 +0200
From: Ertugrul S?ylemez e...@ertes.de
Subject: Re: [Haskell-beginners] FRP and a set of pairwise interacting
(colliding) objects
To: beginners@haskell.org
Message-ID: 20120629164744.0c5cf...@angst.streitmacht.eu
Content-Type: text/plain; charset=utf-8
Nathan H?sken nathan.hues...@posteo.de wrote:
[...]
But now the collisions are generated at one place, and processed at
another. This means that CollData must be somehow tagged to the
objects it belongs to (an ID for example). This again means that some
function must take the pool of all collision datas and distribute them
to the object Signals.
When I have a lot of objects, this means a significant overhead!
Now I am wondering if there is a nicer approach which avoids this
overhead.
You can get around the overhead by letting the objects do the collisions
themselves, much like in your OOP variant. For instance in Netwire you
could have this:
planets :: MyWire [Planet] Planet
This naive way still causes the overhead of lists and a planet
distinguishing between others and itself. But now this is simply a
matter of choosing proper data structures and starting to identify
planets:
type PlanetSet = Map PlanetId Planet
planets :: MyWire PlanetSet (PlanetId, Planet)
This looks more promising. Now the last thing is that this looks like a
chicken/egg problem, but it's easy to resolve using ArrowLoop and
one-instant delays.
Greets,
Ertugrul
--
nightmare = unsafePerformIO (getWrongWife = sex)
http://ertes.de/
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Message: 3
Date: Fri, 29 Jun 2012 11:50:13 -0400
From: Michael Orlitzky mich...@orlitzky.com
Subject: Re: [Haskell-beginners] test-framework
To: beginners@haskell.org
Message-ID: 4fedceb5.2010...@orlitzky.com
Content-Type: text/plain; charset=UTF-8
On 06/29/12 03:58, Mateusz Neumann wrote:
On Fri, 29 Jun
Beginners Digest, Vol 49, Issue 1
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Concurrent vs GHC (Mauricio Hernandes) 2. Re: Concurrent vs GHC (Felipe Almeida Lessa) 3. Re: Concurrent vs GHC (Mauricio Hernandes) -- Message: 1 Date: Sun, 1 Jul 2012 00:03:34 +0900 From: Mauricio Hernandes maukeshig...@gmail.com Subject: [Haskell-beginners] Concurrent vs GHC To: beginners@haskell.org Message-ID: caoons7zurxzpyejxp-wxlutfbx+jdstrhfnvaq2+5w8f9_r...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hello, I'm having a problem with GHC. When I compile the code bellow it does nothing, but If I try to use ghci it works normally. it seems a simple problem, but I can't understand. Thanks for the help Mauricio import System.IO import Control.Concurrent import Data.List main = do input - newMVar [1..3] ia - newEmptyMVar ib - newEmptyMVar ic - newEmptyMVar forkIO $ do x - readMVar input putMVar ia x forkIO $ do a - readMVar ia putMVar ib ( sum a ) forkIO $ do a - readMVar ia putMVar ic ( reverse a ) forkIO $ do b - readMVar ib c - readMVar ic print b print c -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120701/712d04f7/attachment-0001.htm -- Message: 2 Date: Sat, 30 Jun 2012 12:24:02 -0300 From: Felipe Almeida Lessa felipe.le...@gmail.com Subject: Re: [Haskell-beginners] Concurrent vs GHC To: maukeshig...@gmail.com Cc: beginners@haskell.org Message-ID: CANd=ogeerxzpn116cqlpoddvassuebynwrbrg2tp4j3q9ob...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Your application is exiting before your forkIOs get a chance to execute. Instead of forkIO $ do ... forkIO $ do ... forkIO $ do ... use something like finished - newEmptyMVar forkIO $ do ... putMVar finished () forkIO $ do ... putMVar finished () forkIO $ do ... putMVar finished () replicateM_ 3 (takeMVar finished) Doing so will avoid your program to exit until all threads have finished. Note that the code above is extremely fragile: doesn't handle exceptions, you have to manually specify the number of threads that you opened, etc. These are abstracted by some libraries on Hackage that you may use later for Real World Code (TM). Cheers, =) -- Felipe. -- Message: 3 Date: Sun, 1 Jul 2012 02:51:27 +0900 From: Mauricio Hernandes maukeshig...@gmail.com Subject: Re: [Haskell-beginners] Concurrent vs GHC To: Felipe Almeida Lessa felipe.le...@gmail.com Cc: beginners@haskell.org Message-ID: CAOons7a6j9Mws-CTHJvRr5zHFQXmVX7-tpzq=xt0hpnjoej...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Eternal Gratitude for the help, it's working perfectly, I will consider the exceptions and other stuff now. the code looks like this now import System.IO import Control.Concurrent import Data.List import Control.Monad main = do finished - newEmptyMVar input - newMVar [1..3] ia - newEmptyMVar ib - newEmptyMVar ic - newEmptyMVar forkIO $ do x - readMVar input putMVar ia x putMVar finished () forkIO $ do a - readMVar ia putMVar ib ( sum a ) putMVar finished () forkIO $ do a - readMVar ia putMVar ic ( reverse a ) putMVar finished () b - readMVar ib c - readMVar ic writeFile somaEprod.txt (show b ++ \n) appendFile somaEprod.txt (show c) replicateM_ 3 (takeMVar finished) Valeu Mauricio On Sun, Jul 1, 2012 at 12:24 AM, Felipe Almeida Lessa felipe.le...@gmail.com wrote: Your application is exiting before your forkIOs get a chance to execute. Instead of forkIO $ do ... forkIO $ do ... forkIO $ do ... use something like finished - newEmptyMVar forkIO $ do ... putMVar finished () forkIO $ do ... putMVar finished () forkIO $ do ... putMVar finished () replicateM_ 3 (takeMVar finished) Doing so will avoid your program to exit until all threads have finished. Note that the code above is extremely fragile: doesn't handle exceptions, you have to
Beginners Digest, Vol 49, Issue 4
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Today's Topics:
1. Functional Parses (Robert Heum?ller)
2. Re: Functional Parses (Robert Heum?ller)
3. Re: Functional Parses (Christian Maeder)
4. Using tls-extra for simple smtp (Sarfraz K.)
5. Re: Functional Parses (Stephen Tetley)
6. Problems with installing lambdabot (Antoras)
7. Re: Problems with installing lambdabot (Brent Yorgey)
8. Re: Help with Why Do Monads Matter blog post understanding
(Brent Yorgey)
--
Message: 1
Date: Tue, 3 Jul 2012 15:08:37 +0200
From: Robert Heum?ller mail...@heum.de
Subject: [Haskell-beginners] Functional Parses
To: beginners@haskell.org
Message-ID: 20120703150837.34989630@thor
Content-Type: text/plain; charset=US-ASCII
Hi again,
currently I'm trying to figure out how to properly write a parser in
haskell. I've been following the instructions in a book called
Programming in Haskell by Graham Hutton. So far I've written the
following:
--
Message: 2
Date: Tue, 3 Jul 2012 15:16:02 +0200
From: Robert Heum?ller mail...@heum.de
Subject: Re: [Haskell-beginners] Functional Parses
To: beginners@haskell.org
Message-ID: 20120703151602.02384728@thor
Content-Type: text/plain; charset=US-ASCII
I am sorry, I must have hit the wrong hotkey.
My code looks like this:
type Parser a = String - [(a, String)]
result :: a - Parser a
result v = \inp - [(v, inp)]
zero :: Parser a
zero = \inp - []
item :: Parser Char
item = \inp - case inp of
[] - []
(x:xs) - [(x, xs)]
parse :: Parser a - String - [(a, String)]
parse p inp = p inp
(=) :: Parser a - (a - Parser b) - Parser b
(=) p f = \inp - concat [f v inp' | (v, inp') - p inp]
sat :: (Char - Bool) - Parser Char
sat p = do x - item
if p x then result x else zero
I beleive I understand how this code is meant to work, but when I run
it in ghci I get the follwing error-message:
parser.hs:21:13:
No instance for (Monad ((-) String))
arising from a do statement
Possible fix: add an instance declaration for (Monad ((-) String))
In a stmt of a 'do' block: x - item
In the expression:
do { x - item;
if p x then result x else zero }
In an equation for `sat':
sat p
= do { x - item;
if p x then result x else zero }
parser.hs:22:18:
Couldn't match expected type `Char'
with actual type `[(Char, String)]'
In the first argument of `p', namely `x'
In the expression: p x
In a stmt of a 'do' block: if p x then result x else zero
Failed, modules loaded: none.
Sadly I have no idea how to fix this :(
Thanks again :)
--
Message: 3
Date: Tue, 03 Jul 2012 16:13:50 +0200
From: Christian Maeder christian.mae...@dfki.de
Subject: Re: [Haskell-beginners] Functional Parses
To: Robert Heum?ller mail...@heum.de
Cc: beginners@haskell.org
Message-ID: 4ff2fe1e.1040...@dfki.de
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Am 03.07.2012 15:16, schrieb Robert Heum?ller:
I am sorry, I must have hit the wrong hotkey.
My code looks like this:
type Parser a = String - [(a, String)]
This type synonym is unsuitable for a Monad instance.
Better would be:
newtype Parser a = Parser (String - [(a, String)])
but that would require to change your code below.
result :: a - Parser a
result v = \inp - [(v, inp)]
zero :: Parser a
zero = \inp - []
item :: Parser Char
item = \inp - case inp of
[] - []
(x:xs) - [(x, xs)]
parse :: Parser a - String - [(a, String)]
parse p inp = p inp
(=) :: Parser a - (a - Parser b) - Parser b
(=) p f = \inp - concat [f v inp' | (v, inp') - p inp]
Such a definition (without signature and adapted to the newtype) should
be used within a Monad instance. instance Monad Parser where ...
sat :: (Char - Bool) - Parser Char
sat p = do x - item
if p x then result x else zero
Without proper Monad instance you should not use do. Instead you could
expand it yourself manually to:
sat p = item Main.= \x -
if p x then result x else zero
Note the clash between your = function (Main.=) and the one from
the Prelude!
HTH Christian
P.S. there is a instance Monad ((-) r)) in Control.Monad.Instances
but that does not fit your parser type, too.
I beleive I understand how this code is meant to work, but when I run
it in ghci I get the follwing error-message:
parser.hs:21:13:
No instance for (Monad
Beginners Digest, Vol 49, Issue 5
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Problems with installing lambdabot (Brandon Allbery) 2. Re: Functional Parses (Robert Heum?ller) 3. Re: Functional Parses (Brandon Allbery) 4. Re: Problems with installing lambdabot (Antoras) 5. Re: Problems with installing lambdabot (Brent Yorgey) 6. Re: Problems with installing lambdabot (Brent Yorgey) -- Message: 1 Date: Tue, 3 Jul 2012 15:47:30 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] Problems with installing lambdabot To: Antoras m...@antoras.de Cc: beginners@haskell.org Message-ID: CAKFCL4UD8D10S2SHrv+nDBiW0=9-f7K97d4g6cSb-=9kch5...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Tue, Jul 3, 2012 at 3:16 PM, Antoras m...@antoras.de wrote: Loading package readline-1.0.1.0 ... command line: can't load .so/.DLL for: /usr/lib/gcc/x86_64-unknown-**linux-gnu/4.7.1/../../../../**lib/libncurses.so (-lncursesw: cannot open shared object file: No such file or directory) Your Linux distribution pulled a cute stunt that throws the dynamic loader (used for TH and ghci and a few other things) for a loop: libncurses.so, for backward compatibility purposes, is a GNU ld linker script which references libncursesw.so in a way the dynamic loader doesn't understand. You can work around this in one of two ways: 1. replace /usr/lib/libncurses.so with a symlink to /usr/lib/libncursesw.so; OR 2. edit /usr/lib/libncurses.so, which is a text file (linker script), to reference /usr/lib/libncursesw.so instead of -lncursesw. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120703/9d8c9339/attachment-0001.htm -- Message: 2 Date: Tue, 3 Jul 2012 23:02:21 +0200 From: Robert Heum?ller mail...@heum.de Subject: Re: [Haskell-beginners] Functional Parses To: beginners@haskell.org Message-ID: 20120703230221.4df7aeff@thor Content-Type: text/plain; charset=US-ASCII Thank you very much. I'll check out the code on the website tomorrow and hopefully this will solve the problem. Whenever monads apper things seem to get tricky - sadly there won't be a lecture on functional programming in the next semester at the university I study at :( Am Tue, 3 Jul 2012 18:01:32 +0100 schrieb Stephen Tetley stephen.tet...@gmail.com: On 3 July 2012 15:13, Christian Maeder christian.mae...@dfki.de wrote: This type synonym is unsuitable for a Monad instance. Better would be: newtype Parser a = Parser (String - [(a, String)]) but that would require to change your code below. This is alluded to in the closing chapter remarks (section 8.9) of Graham Hutton's book and there is code available on the website that accompanies the book that solves the problem. Unfortunately, this chapter does seem to trip people up who use the book for self study. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Tue, 3 Jul 2012 17:09:20 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] Functional Parses To: Robert Heum?ller mail...@heum.de Cc: beginners@haskell.org Message-ID: cakfcl4uz0huk4sq+j8xecc6tvcpqntg_hxmwgxifkueo06r...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Tue, Jul 3, 2012 at 5:02 PM, Robert Heum?ller mail...@heum.de wrote: Whenever monads apper things seem to get tricky - sadly there won't be a lecture on functional programming in the next semester at the university I study at :( The only trick here is that the text wants to introduce you to monads by doing something that won't work in a normal Haskell; you need to put the compiler in a mode which allows you to in effect rebuild them from scratch. (You can't simply provide your own definitions because do notation is hardwired to use the standard ones anyway, unless you use the RebindableSyntax extension to tell it to use yours. You'd also have to make sure you don't get the standard definitions, which means NoImplicitPrelude and manually importing Prelude minus the standard machinery. I don't think RebindableSyntax let you rebind do notation properly
Beginners Digest, Vol 49, Issue 6
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. What's this [f| data |] ?? (Carlos J. G. Duarte) 2. Re: What's this [f| data |] ?? (Jack Henahan) 3. Re: What's this [f| data |] ?? (David McBride) 4. Re: What's this [f| data |] ?? (Brent Yorgey) 5. Re: What's this [f| data |] ?? (Felipe Almeida Lessa) 6. Re: What's this [f| data |] ?? (Felipe Almeida Lessa) 7. Re: Using tls-extra for simple smtp (Henk-Jan van Tuyl) -- Message: 1 Date: Wed, 04 Jul 2012 03:10:59 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: [Haskell-beginners] What's this [f| data |] ?? To: beginners@haskell.org Message-ID: 4ff3a633.8020...@gmail.com Content-Type: text/plain; charset=iso-8859-1; Format=flowed Hi. I'm trying to get into haskell in my free time. I have already covered some syntax, but there's plenty to do yet, and when I'm consulting other people's stuff, I find lots of unknown constructs to me, which turns harder to lookup for, due to the very symbolic nature of Haskell. For instance, on this http://www.yesodweb.com/blog/2012/04/yesod-js-todo they have a few constructs like this: |mkYesod App [parseRoutes| /HomeR GET /todoTodosR GET PUT /todo/#TodoId TodoR GET DELETE |]| It seems that the inline text is going to be fed to parseRoutes. How does that constructs work (links?)? I already know list comprehensions which appear to be related with this. Thanks. -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120704/dcef6919/attachment-0001.htm -- Message: 2 Date: Tue, 3 Jul 2012 22:30:58 -0400 From: Jack Henahan jhena...@uvm.edu Subject: Re: [Haskell-beginners] What's this [f| data |] ?? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: db99b310-c54e-4362-8d3b-65a7e333e...@uvm.edu Content-Type: text/plain; charset=iso-8859-1 parseRoutes is a quasiquoter [1]. It uses a type-safe metaprogramming language called Template Haskell [2] to parse a string as a Route (e.g., HomeR is a Route describing the base resource). You can see the source here [3]. I'm pretty new with Yesod, myself, so I'm sure someone else will give you a more in depth description shortly. [1]: http://www.haskell.org/haskellwiki/Quasiquotation [2]: http://www.haskell.org/haskellwiki/Template_Haskell [3]: http://hackage.haskell.org/packages/archive/yesod-routes/1.0.1.2/doc/html/src/Yesod-Routes-Parse.html#parseRoutes On Jul 3, 2012, at 10:10 PM, Carlos J. G. Duarte wrote: Hi. I'm trying to get into haskell in my free time. I have already covered some syntax, but there's plenty to do yet, and when I'm consulting other people's stuff, I find lots of unknown constructs to me, which turns harder to lookup for, due to the very symbolic nature of Haskell. For instance, on this http://www.yesodweb.com/blog/2012/04/yesod-js-todo they have a few constructs like this: mkYesod App [parseRoutes| / HomeR GET /todo TodosR GET PUT /todo/# TodoId TodoR GET DELETE |] It seems that the inline text is going to be fed to parseRoutes. How does that constructs work (links?)? I already know list comprehensions which appear to be related with this. Thanks. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 841 bytes Desc: Message signed with OpenPGP using GPGMail URL: http://www.haskell.org/pipermail/beginners/attachments/20120703/3f3913a6/attachment-0001.pgp -- Message: 3 Date: Tue, 3 Jul 2012 22:32:28 -0400 From: David McBride toa...@gmail.com Subject: Re: [Haskell-beginners] What's this [f| data |] ?? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: CAN+Tr40i2kX371kKcH0Gb30Afw8-fne=4MK+kNy1c7Jj6z+=c...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 This is quasiquoting. It is a pretty advanced topic, but it allows you to take an arbitrary string and parse it with a quasiquoter of your choice (in this case, parseRoutes) into some structure or another. Yesod uses it all over the place to generate html, javascript, routing tables, and such. On Tue, Jul 3, 2012 at 10:10
Beginners Digest, Vol 49, Issue 7
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Comments on Map/Reduce Code (Thomas Bach) 2. arbitrary rank polymorphism and ghc language pragmas (rickmurphy) 3. Re: [Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas (rickmurphy) 4. Expert systems using Haskell (Ramesh Kumar) -- Message: 1 Date: Thu, 5 Jul 2012 15:50:32 +0200 From: Thomas Bach thb...@students.uni-mainz.de Subject: [Haskell-beginners] Comments on Map/Reduce Code To: beginners@haskell.org Message-ID: 87ipe2mi53@roku.box Content-Type: text/plain; charset=utf-8 Hello there, I'm new to Haskell and want to learn it a bit while experimenting with Hadoop's Map/Reduce programming model. So, I wanted to implement the standard ?word counter? problem in Haskell. The problem is as follows: We have several texts with words separated by white-space. We want to count the occurrences of all words in all the texts (where ?but? and ?but,? can be seen as two different words). This is done in two phases. In the Map phase a program gets a part of the text from stdout and has to produce a KEY\tVALUE pair (that is, the key separated with a tab to the value), which has to be passed to stdin. In our case we simply produce WordX\t1 for every word WordX. This list is sorted by the key and later on fed as stdin to the reducer (the second phase). The reducer now has to sum up all the occurrences we trivially counted in the Map phase and put it as WordX\tNumber to stdout. So, here is an example: vince@roku:~/tmp echo foo foo bar bar foo bar zoo bar foo | runhaskell mapper.hs foo 1 foo 1 bar 1 bar 1 foo 1 bar 1 zoo 1 bar 1 foo 1 vince@roku:~/tmp echo foo foo bar bar foo bar zoo bar foo | runhaskell mapper.hs | sort | runhaskell reducer.hs bar 4 foo 4 zoo 1 And here is the code I've come up with: vince@roku:~/tmp cat mapper.hs import qualified Data.ByteString.Lazy.Char8 as C postFix :: C.ByteString postFix = C.pack \t1 formatter :: C.ByteString - C.ByteString formatter x = C.append x postFix main :: IO () main = do contents - fmap C.words C.getContents C.putStr . C.unlines $ map formatter contents vince@roku:~/tmp cat reducer.hs import qualified Data.ByteString.Lazy.Char8 as C import qualified Data.List as L tuppleize :: String - (String, Int) tuppleize line = (\xs - (head xs, read (last xs))) $ words line group :: Eq a = [(a, b)] - [[(a, b)]] group = L.groupBy (\x y - fst x == fst y) summation :: Num b = [(a, b)] - (a, b) summation (x:[]) = x summation (x:xs) = (fst x, (snd x) + (snd (summation xs))) formatter :: (String, Int) - String formatter = (\w - (fst w ++ \t ++ show (snd w))) main = do contents - C.getContents putStr . unlines $ map formatter $ map summation $ group $ map tuppleize $ lines $ C.unpack contents As already said, I'm a Haskell beginner. Could you provide some comments on the code? Thanks in advance, Thomas. -- Message: 2 Date: Thu, 05 Jul 2012 11:18:00 -0400 From: rickmurphy r...@rickmurphy.org Subject: [Haskell-beginners] arbitrary rank polymorphism and ghc languagepragmas To: beginners beginners@haskell.org, haskell-c...@haskell.org Message-ID: 1341501480.13998.36.camel@metho-laptop Content-Type: text/plain; charset=UTF-8 Hi All: I've been working through some details in these papers [1], [2] and noticed a language pragma configuration that I hope you can confirm. When using explicit foralls in a data constructor, it appears that GHC 7.4.2 requires Rank2Types in the Language pragma for what the papers consider rank 1 types. Here's an example: data T = TC (forall a b. a - b - a) Am I correct, or is there another extension? The ExplicitForAll does not appear to support rank 1 types in data constructors. 1. Practical Type Inference for Arbitrary-Rank Types. 2. A Direct Algorithm for Type Inference in the Rank 2 Fragment of the Second-Order Lambda Calculus. -- Rick -- Message: 3 Date: Thu, 05 Jul 2012 13:17:12 -0400 From: rickmurphy r...@rickmurphy.org Subject: Re: [Haskell-beginners] [Haskell-cafe] arbitrary rank polymorphism and ghc language pragmas To: beginners beginners@haskell.org, haskell-c...@haskell.org Message-ID: 1341508632.14924.3.camel@metho-laptop Content-Type: text/plain; charset=UTF-8 Thanks Francesco. And I did verify
Beginners Digest, Vol 49, Issue 11
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Comments on Map/Reduce Code (Brent Yorgey) 2. Trouble compiling haskell platfrom (Jeff Lasslett) -- Message: 1 Date: Tue, 10 Jul 2012 10:19:48 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Comments on Map/Reduce Code To: beginners@haskell.org Message-ID: 20120710141948.ga16...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Thu, Jul 05, 2012 at 03:50:32PM +0200, Thomas Bach wrote: Hello there, Hi Thomas, Looks pretty good. I've interspersed a few comments below. And here is the code I've come up with: vince@roku:~/tmp cat mapper.hs import qualified Data.ByteString.Lazy.Char8 as C postFix :: C.ByteString postFix = C.pack \t1 formatter :: C.ByteString - C.ByteString formatter x = C.append x postFix main :: IO () main = do contents - fmap C.words C.getContents C.putStr . C.unlines $ map formatter contents The above looks fine, except that generally the recommendation is to use the text package [1] for dealing with text, whereas ByteString is for binary data that you wish to manipulate as a sequence of bytes. You can get away with the above only when the text consists entirely of ASCII characters. [1] http://hackage.haskell.org/package/text vince@roku:~/tmp cat reducer.hs import qualified Data.ByteString.Lazy.Char8 as C import qualified Data.List as L tuppleize :: String - (String, Int) tuppleize line = (\xs - (head xs, read (last xs))) $ words line What happens when the line is empty? group :: Eq a = [(a, b)] - [[(a, b)]] group = L.groupBy (\x y - fst x == fst y) The above lambda can also be written as ((==) `on` fst). 'on' can be imported from Data.Function. summation :: Num b = [(a, b)] - (a, b) summation (x:[]) = x summation (x:xs) = (fst x, (snd x) + (snd (summation xs))) Instead of using (fst x) and (snd x), you should pattern-match on x, like summation ((x,y):xs) = (x, y + ...) formatter :: (String, Int) - String formatter = (\w - (fst w ++ \t ++ show (snd w))) The same goes here. I would also put the w argument on the left-hand side of the =, like formatter (s,i) = s ++ \t ++ show i main = do contents - C.getContents putStr . unlines $ map formatter $ map summation $ group $ map tuppleize $ lines $ C.unpack contents Instead of using a chain of ($), it's generally considered better style to use a chain of (.) with a single $ at the end, like putStr . unlines . map formatter ... lines . C.unpack $ contents -Brent -- Message: 2 Date: Wed, 11 Jul 2012 10:07:38 +1000 From: Jeff Lasslett jeff.lassl...@gmail.com Subject: [Haskell-beginners] Trouble compiling haskell platfrom To: Beginners@haskell.org Message-ID: CAK6+hbxU5k=p0-3myvxf6j5xvao9lta7fkrg2kotvv6wtrp...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Greetings, I'm trying to recompile reinstall the haskell platform 12.2.0.0. I have installed it successfully on a prior occasion but I decided to reinstall as I think I may have messed up my installed packages a bit while playing around with yesod. I intend to use cabal-dev or virtualenv for that in future. So I thought I'd do a clean install. I blew away my haskell platform and ghc, both of which were installed in a dir under my home dir. I also blew away my ~/.cabal/ dir. I then reinstalled by ghc 7.4.1 into ~/prg/haskell-platform-12.2.0.0. I then unpacked the sources of haskell-platform-12.2.0.0 and configured it with the prefix set to where ghc is. configure finished without error so I ran 'make'. It quits with what follows. How do I fix this?? With thanks, Jeff * Now do make followed by make install ** jeff@chunks:~/src/haskell-platform-2012.2.0.0$ make scripts/build.sh ** Scanning system for any installed Haskell Platform components... Found: HUnit-1.2.4.2 OpenGL-2.2.3.1 GLUT-2.1.2.1 html-1.0.1.2 parallel-3.2.0.2 random-1.0.1.1 QuickCheck-2.4.2 stm-2.3 syb-0.3.6.1 haskell-src-1.0.1.5 text-0.11.2.0 transformers-0.3.0.0 mtl-2.1.1 fgl-5.4.2.4 parsec-3.1.2 network-2.3.0.13 HTTP-4000.2.3 regex-base-0.93.2 regex-posix-0.95.1 regex-compat-0.95.1 xhtml-3000.2.1 cgi-3001.1.7.4 zlib-0.5.3.3 haskell-platform-2012.2.0.0 New packages to install: None! All done. ** Building alex-3.0.1
Beginners Digest, Vol 49, Issue 12
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Trouble compiling haskell platfrom (gdwe...@iue.edu) 2. Re: Trouble compiling haskell platfrom (Jeff Lasslett) 3. Re: Concurrent vs GHC (Mauricio Hernandes) 4. Hackage down? (Lorenzo Bolla) -- Message: 1 Date: Wed, 11 Jul 2012 16:48:13 -0400 From: gdwe...@iue.edu Subject: Re: [Haskell-beginners] Trouble compiling haskell platfrom To: Jeff Lasslett jeff.lassl...@gmail.com Cc: Beginners@haskell.org Message-ID: 20120711204813.gg...@tramp.ftrdhcpuser.net Content-Type: text/plain; charset=us-ascii Hi, On 2012-Jul-11, Jeff Lasslett wrote: Greetings, I'm trying to recompile reinstall the haskell platform 12.2.0.0. I have installed it successfully on a prior occasion but I decided to reinstall as I think I may have messed up my installed packages a bit while playing around with yesod. I intend to use cabal-dev or virtualenv for that in future. So I thought I'd do a clean install. I blew away my haskell platform and ghc, both of which were installed in a dir under my home dir. I also blew away my ~/.cabal/ dir. I then reinstalled by ghc 7.4.1 into ~/prg/haskell-platform-12.2.0.0. I then unpacked the sources of haskell-platform-12.2.0.0 and configured it with the prefix set to where ghc is. configure finished without error so I ran 'make'. It quits with what follows. How do I fix this?? With thanks, Jeff * Now do make followed by make install ** jeff@chunks:~/src/haskell-platform-2012.2.0.0$ make scripts/build.sh ** Scanning system for any installed Haskell Platform components... Found: HUnit-1.2.4.2 OpenGL-2.2.3.1 GLUT-2.1.2.1 html-1.0.1.2 parallel-3.2.0.2 random-1.0.1.1 QuickCheck-2.4.2 stm-2.3 syb-0.3.6.1 haskell-src-1.0.1.5 text-0.11.2.0 transformers-0.3.0.0 mtl-2.1.1 fgl-5.4.2.4 parsec-3.1.2 network-2.3.0.13 HTTP-4000.2.3 regex-base-0.93.2 regex-posix-0.95.1 regex-compat-0.95.1 xhtml-3000.2.1 cgi-3001.1.7.4 zlib-0.5.3.3 haskell-platform-2012.2.0.0 New packages to install: None! All done. ** Building alex-3.0.1 /home/jeff/prg/haskell-platform-12.2.0.0/bin/ghc --make Setup -o Setup -package Cabal-1.14.0 Linking Setup ... ./Setup configure --package-db=../../packages/package.conf.inplace --prefix=/home/jeff/prg/haskell-platform-12.2.0.0 --with-compiler=/home/jeff/prg/haskell-platform-12.2.0.0/bin/ghc --with-hc-pkg=/home/jeff/prg/haskell-platform-12.2.0.0/bin/ghc-pkg --with-hsc2hs=/home/jeff/prg/haskell-platform-12.2.0.0/bin/hsc2hs --enable-library-profiling --ghc-pkg-option=--package-conf=../../packages/package.conf.inplace --user Warning: defaultUserHooks in Setup script is deprecated. Configuring alex-3.0.1... ./Setup build Building alex-3.0.1... Preprocessing executable 'alex' for alex-3.0.1... src/Data/Ranged/RangedSet.hs:64:8: Could not find module `Test.QuickCheck' There are files missing in the `QuickCheck-2.4.2' package, try running 'ghc-pkg check'. Use -v to see a list of the files searched for. I would suggest start by doing what it says just above: run `ghc-pkg check`. This will give you a list of broken packages. For each such package `P`, run `ghc-pkg unregister P`. Then you can try installing Haskell Platform again, starting with the configure step. For a detailed explanation of what's going on here, see Albert Lai's Storage and Identification of Cabalized Packages: http://www.vex.net/~trebla/haskell/sicp.xhtml Error: Building the alex-3.0.1 package failed make: *** [build.stamp] Error 2 ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Gregory D. Weber, Ph. D.: Associate Professor of Informatics / \ Indiana University East 0 : Tel. (765) 973-8420; FAX (765) 973-8550 / \ http://mypage.iu.edu/~gdweber/ 1 [] -- Message: 2 Date: Thu, 12 Jul 2012 14:01:12 +1000 From: Jeff Lasslett jeff.lassl...@gmail.com Subject: Re: [Haskell-beginners] Trouble compiling haskell platfrom To: gdwe...@iue.edu Cc: Beginners@haskell.org Message-ID: cak6+hby1quu6ssf8u2oh_pnyb3dcbvl65m5r++3krm6c1tn...@mail.gmail.com Content-Type:
Beginners Digest, Vol 49, Issue 13
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Hackage down? (Mauricio Hernandes) 2. Re: Hackage down? (Brent Yorgey) -- Message: 1 Date: Thu, 12 Jul 2012 23:51:39 +0900 From: Mauricio Hernandes maukeshig...@gmail.com Subject: Re: [Haskell-beginners] Hackage down? To: Lorenzo Bolla lbo...@gmail.com Cc: beginners@haskell.org Message-ID: CAOons7a9k6KGxDpywZwHY7hSb9AZ6qmiZGsC=rcv-auogxj...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I had the same problem today :( but I think at least hoogle is working already \o/ On Thu, Jul 12, 2012 at 4:51 PM, Lorenzo Bolla lbo...@gmail.com wrote: Is hackage.haskell.org down? cabal update times out here... How do you guys work around this? It seems to happen pretty often. L. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120712/93a06915/attachment-0001.htm -- Message: 2 Date: Thu, 12 Jul 2012 11:29:42 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Hackage down? To: beginners@haskell.org Message-ID: 20120712152942.ga9...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii Looks like Hackage is back up now. The official word is that something (not sure what yet) was hitting the server really hard and causing the load average to go through the roof, and it had to be rebooted. For future reference, an up-to-date mirror of the packages is maintained at http://hdiff.luite.com/packages/archive/ -Brent On Thu, Jul 12, 2012 at 08:51:48AM +0100, Lorenzo Bolla wrote: Is hackage.haskell.org down? cabal update times out here... How do you guys work around this? It seems to happen pretty often. L. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 49, Issue 13 *
Beginners Digest, Vol 49, Issue 16
Send Beginners mailing list submissions to
beginners@haskell.org
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http://www.haskell.org/mailman/listinfo/beginners
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than Re: Contents of Beginners digest...
Today's Topics:
1. Review request (C K Kashyap)
2. I can see lists working for matrix algorithms if the
access patterns are mostly from the start or end of rows and
columns. (KC)
3. DPH installation and LLVM (listig...@gmail.com)
4. Re: DPH installation and LLVM (Brandon Allbery)
5. Re: Review request (Carlos J. G. Duarte)
6. Re: DPH installation and LLVM (listig...@gmail.com)
--
Message: 1
Date: Sun, 15 Jul 2012 17:38:29 +0530
From: C K Kashyap ckkash...@gmail.com
Subject: [Haskell-beginners] Review request
To: beginners beginners@haskell.org
Message-ID:
CAGdT1goLUM8TxA=ntyuvmpdyackf5m_c6_jb7fmu5-zmerw...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
Hi,
I've written a small haskell program to extract a section from a file
between start and end markers. For example, if I have a file such as below
-
a
b
c
bug
d
e
f
/bug
g
h
i
I'd like to extract the contents between bug and /bug (including the
markers).
startTag = bugendTag = /bug
process = unlines . specialTakeWhile (f endTag) . dropWhile (f
startTag) . lines
where f t x = not (x =~ t)
specialTakeWhile :: (a - Bool) - [a] - [a]
specialTakeWhile ff [] = []
specialTakeWhile ff (x:xs) = if ff x then
x:(specialTakeWhile ff xs) else [x]
It'll be great if I could get some feedback on this.
Regards,
Kashyap
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Message: 2
Date: Sun, 15 Jul 2012 11:01:40 -0700
From: KC kc1...@gmail.com
Subject: [Haskell-beginners] I can see lists working for matrix
algorithms if the access patterns are mostly from the start or end of
rows and columns.
To: haskell-cafe haskell-c...@haskell.org, beginners@haskell.org
Message-ID:
CAMLKXynLpMEEh8ZEZe0c07WSJP=jbwwbxesuoqf2bc2pdbv...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
Are there any such matrix algorithms that operate mainly from the start or
end or rows and columns?
Note: If the access pattern starts from the end of a row then one stores
the row in reverse order in a list.
--
--
Regards,
KC
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Message: 3
Date: Sun, 15 Jul 2012 14:49:47 -0400
From: listig...@gmail.com
Subject: [Haskell-beginners] DPH installation and LLVM
To: beginners@haskell.org
Message-ID: c418f1b4-4131-43a1-8799-492884b13...@gmail.com
Content-Type: text/plain; charset=us-ascii
Dear all,
being completely new to Haskell I wanted to explore what DPH is about, so I
tried to install it via
cabal install dph-examples
but the installation process stops once it gets to installing the actual
examples package:
---
Building dph-examples-0.6.1.3...
Preprocessing executable 'dph-spectral-smvm' for dph-examples-0.6.1.3...
[1 of 3] Compiling Vectorised ( examples/spectral/SMVM/dph/Vectorised.hs,
dist/build/dph-spectral-smvm/dph-spectral-smvm-tmp/Vectorised.o )
exprType TYPE ghc-prim:GHC.Types.Double{(w) tc 3u}
exprType TYPE ghc-prim:GHC.Types.Double{(w) tc 3u}
exprType TYPE ghc-prim:GHC.Types.Double{(w) tc 3u}
exprType TYPE ghc-prim:GHC.Types.Double{(w) tc 3u}
exprType TYPE ghc-prim:GHC.Types.Double{(w) tc 3u}
exprType
TYPE (ghc-prim:GHC.Types.Int{(w) tc 3J},
ghc-prim:GHC.Types.Double{(w) tc 3u})
Warning: Couldn't figure out LLVM version!
Make sure you have installed LLVM
ghc: could not execute: opt
cabal: Error: some packages failed to install:
dph-examples-0.6.1.3 failed during the building phase. The exception was:
ExitFailure 1
---
This is the rest of my setup:
Mac OS X 10.7.4
Xcode 4.3.3 + Command Line Tools (from within Xcode)
Haskell Platform 2012.2.0.0 32bit
Why doesn't Haskell find the LLVM compiler? Is there a way to install the
remaining examples without LLVM compilation?
Thanks,
Oliver
--
Message: 4
Date: Sun, 15 Jul 2012 14:56:32 -0400
From: Brandon Allbery allber...@gmail.com
Subject: Re: [Haskell-beginners] DPH installation and LLVM
To: listig...@gmail.com
Cc: beginners@haskell.org
Message-ID:
Beginners Digest, Vol 49, Issue 18
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Review request (C K Kashyap) 2. Re: Review request (Carlos J. G. Duarte) -- Message: 1 Date: Mon, 16 Jul 2012 16:40:45 +0530 From: C K Kashyap ckkash...@gmail.com Subject: Re: [Haskell-beginners] Review request To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: cagdt1govmw+mimmmq-xcejzdwcx1uzrf+w11pdmuembafsa...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Thanks Carlos - you can import Text.Regex.Posix to get (=~) Is there a way to avoid the (++) in your implementation? It has a linear time overhead. Regards, Kashyap On Mon, Jul 16, 2012 at 1:36 AM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: Looks good to me, but I'm just a beginner! I used the isInfixOf from Data.List instead of =~ to run your example because the later wasn't working on my instalation. I've made a slightly variant using the break function: import Data.List startTag = bug endTag = /bug main = interact process process = unlines . extractSection startTag endTag . lines extractSection start stop xs = let (ls,rs) = break (isInfixOf stop) $ dropWhile (not . isInfixOf start) xs in ls ++ take 1 rs On 07/15/12 13:08, C K Kashyap wrote: Hi, I've written a small haskell program to extract a section from a file between start and end markers. For example, if I have a file such as below - a b c bug d e f /bug g h i I'd like to extract the contents between bug and /bug (including the markers). startTag = bugendTag = /bug process = unlines . specialTakeWhile (f endTag) . dropWhile (f startTag) . lines where f t x = not (x =~ t) specialTakeWhile :: (a - Bool) - [a] - [a] specialTakeWhile ff [] = [] specialTakeWhile ff (x:xs) = if ff x then x:(specialTakeWhile ff xs)** else [x] It'll be great if I could get some feedback on this. Regards, Kashyap ___ Beginners mailing listBeginners@haskell.orghttp://www.haskell.org/mailman/listinfo/beginners ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120716/491783ee/attachment-0001.htm -- Message: 2 Date: Mon, 16 Jul 2012 17:57:59 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: Re: [Haskell-beginners] Review request To: beginners@haskell.org Message-ID: 50044817.1000...@gmail.com Content-Type: text/plain; charset=us-ascii An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120716/7a39c0a5/attachment-0001.htm -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 49, Issue 18 *
Beginners Digest, Vol 49, Issue 20
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Simon Peter Nicholls) 2. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Brent Yorgey) 3. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Sylvain HENRY) 4. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Simon Peter Nicholls) 5. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Sylvain HENRY) 6. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Simon Peter Nicholls) -- Message: 1 Date: Wed, 18 Jul 2012 15:14:46 +0200 From: Simon Peter Nicholls si...@mintsource.org Subject: [Haskell-beginners] How do I marshall a pointer over SendMessage LPARAM or WPARAM? To: beginners@haskell.org Message-ID: caeacojkqwr69jueswg5te4fq1p2nszo2cqrtdqbbyevye7p...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I'm new to Haskell, and have had some good success with FFI so far, but using Win32's sendMessage to send a pointer in LPARAM or WPARAM is resulting in access violations at the other end. Is there some issue with my pointer conversions? Am I hitting some restriction, or missing some compiler options? It's driving me pretty crazy, after a very nice start to using Haskell. Some sending code: Foreign.C.String.withCWString frustrator $ \s - do let wParam = System.Win32.Types.castPtrToUINT s :: System.Win32.Types.WPARAM Graphics.Win32.sendMessage wnd Graphics.Win32.wM_APP wParam 0 wndProc receiving code: | wmsg == Graphics.Win32.wM_APP = do s - peekCWString $ System.Win32.Types.castUINTToPtr wParam putStrLn s return 0 The string will not be seen. Some extra notes: I can get wndProc messages and integral data generally. The pointer values match textually at both ends when shown to stdout. At the sending side I can pass the CWString to a regular FFI function call just fine, and castUINTToPtr will give me back a functioning Ptr for that call. I have also tried sending to receiving from a working C++ program, without success. Access violations are reported when receiving, though again the address matches up. Silence from Haskell as before, when C++ is sending. I found someone else having an issue here: http://osdir.com/ml/haskell-c...@haskell.org/2009-11/msg00731.html but no solution unfortunately. -- Message: 2 Date: Wed, 18 Jul 2012 11:47:40 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] How do I marshall a pointer over SendMessage LPARAM or WPARAM? To: beginners@haskell.org Message-ID: 20120718154740.ga27...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii Hi, Just a meta-comment: this doesn't seem like a beginner question to me. =) Perhaps someone on this list will know the answer (and there's nothing wrong with asking), but for such a specific question you may have better luck posting to haskell-cafe or StackOverflow. -Brent On Wed, Jul 18, 2012 at 03:14:46PM +0200, Simon Peter Nicholls wrote: I'm new to Haskell, and have had some good success with FFI so far, but using Win32's sendMessage to send a pointer in LPARAM or WPARAM is resulting in access violations at the other end. Is there some issue with my pointer conversions? Am I hitting some restriction, or missing some compiler options? It's driving me pretty crazy, after a very nice start to using Haskell. Some sending code: Foreign.C.String.withCWString frustrator $ \s - do let wParam = System.Win32.Types.castPtrToUINT s :: System.Win32.Types.WPARAM Graphics.Win32.sendMessage wnd Graphics.Win32.wM_APP wParam 0 wndProc receiving code: | wmsg == Graphics.Win32.wM_APP = do s - peekCWString $ System.Win32.Types.castUINTToPtr wParam putStrLn s return 0 The string will not be seen. Some extra notes: I can get wndProc messages and integral data generally. The pointer values match textually at both ends when shown to stdout. At the sending side I can pass the CWString to a regular FFI function call just fine, and castUINTToPtr will give me back a functioning Ptr for that call. I have also tried sending to receiving from a working C++ program, without success. Access
Beginners Digest, Vol 49, Issue 21
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Sylvain HENRY) 2. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Simon Peter Nicholls) 3. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Simon Peter Nicholls) 4. Re: haskell for system administration (Erik Johnson) -- Message: 1 Date: Wed, 18 Jul 2012 19:13:00 +0200 From: Sylvain HENRY hsy...@gmail.com Subject: Re: [Haskell-beginners] How do I marshall a pointer over SendMessage LPARAM or WPARAM? To: beginners@haskell.org Message-ID: 5006ee9c.5060...@gmail.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed If you are doing inter-process communication, you should not send pointers as processes do not share the same address space. Use WM_COPYDATA to send a specific amount of data. http://msdn.microsoft.com/en-us/library/windows/desktop/ms649011%28v=vs.85%29.aspx I've read that SendMessage is blocking, so you can use withCWString (contrary to what I have previously written). As you have to pass the size of the data, you can even use withCWStringLen (and peekCWStringLen). Cheers Sylvain Le 18/07/2012 19:02, Simon Peter Nicholls a ?crit : It's inter-process by design. I have a small single instance C++ program that I'm porting to Haskell. Once the first instance launched is up and running, subsequent launches send their command line params through to the single instance (file names). Similar to when a media player queues files in a play list. The most recent extra clue I have is that if I wrap the SendMessage function with my own C FFI version, my C function can both re-cast and output the CWString I have sent, and can successfully invoke the real SendMessage by overriding the CWString with a newly created Lblah string. It's just a shame it can't use the original! My next session will involve poking around at the two strings to learn why they are treated differently. On Wed, Jul 18, 2012 at 6:33 PM, Sylvain HENRY hsy...@gmail.com wrote: Are you sending the message to a window of the same process? -Sylvain Le 18/07/2012 18:28, Simon Peter Nicholls a ?crit : I've tried that without joy. Have reposted over at Haskell cafe, as per Brent's advice. Thanks to both of you. On Wed, Jul 18, 2012 at 5:56 PM, Sylvain HENRY hsy...@gmail.com wrote: Hi, [As I've just registered to the list, I don't have the original message. That's why I answer to Brent insted of Simon] By using withCWString, your CWString may be freed before the message is sent. Use newCWString instead and free in your receiving code. Cheers Sylvain Le 18/07/2012 17:47, Brent Yorgey a ?crit : Hi, Just a meta-comment: this doesn't seem like a beginner question to me. =) Perhaps someone on this list will know the answer (and there's nothing wrong with asking), but for such a specific question you may have better luck posting to haskell-cafe or StackOverflow. -Brent On Wed, Jul 18, 2012 at 03:14:46PM +0200, Simon Peter Nicholls wrote: I'm new to Haskell, and have had some good success with FFI so far, but using Win32's sendMessage to send a pointer in LPARAM or WPARAM is resulting in access violations at the other end. Is there some issue with my pointer conversions? Am I hitting some restriction, or missing some compiler options? It's driving me pretty crazy, after a very nice start to using Haskell. Some sending code: Foreign.C.String.withCWString frustrator $ \s - do let wParam = System.Win32.Types.castPtrToUINT s :: System.Win32.Types.WPARAM Graphics.Win32.sendMessage wnd Graphics.Win32.wM_APP wParam 0 wndProc receiving code: | wmsg == Graphics.Win32.wM_APP = do s - peekCWString $ System.Win32.Types.castUINTToPtr wParam putStrLn s return 0 The string will not be seen. Some extra notes: I can get wndProc messages and integral data generally. The pointer values match textually at both ends when shown to stdout. At the sending side I can pass the CWString to a regular FFI function call just fine, and castUINTToPtr will give me back a functioning Ptr for that call. I have also tried sending to receiving from a working C++ program, without success. Access violations are reported when receiving, though again the address matches up.
Beginners Digest, Vol 49, Issue 22
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: How do I marshall a pointer over SendMessage LPARAM or WPARAM? (Brent Yorgey) 2. Where do you put your tests? (Lorenzo Bolla) -- Message: 1 Date: Wed, 18 Jul 2012 16:28:09 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] How do I marshall a pointer over SendMessage LPARAM or WPARAM? To: beginners@haskell.org Message-ID: 20120718202809.ga11...@seas.upenn.edu Content-Type: text/plain; charset=iso-8859-1 I'm very glad to have been proven wrong about someone on the beginners list being able to help. =) On Wed, Jul 18, 2012 at 09:40:51PM +0200, Simon Peter Nicholls wrote: Well, I couldn't wait until tomorrow of course. I just had to have an after-dinner hack, tried again with WM_COPYDATA / COPYDATASTRUCT, and it worked first time! Thanks again for your help! On Wed, Jul 18, 2012 at 7:13 PM, Sylvain HENRY hsy...@gmail.com wrote: If you are doing inter-process communication, you should not send pointers as processes do not share the same address space. Use WM_COPYDATA to send a specific amount of data. http://msdn.microsoft.com/en-us/library/windows/desktop/ms649011%28v=vs.85%29.aspx I've read that SendMessage is blocking, so you can use withCWString (contrary to what I have previously written). As you have to pass the size of the data, you can even use withCWStringLen (and peekCWStringLen). Cheers Sylvain Le 18/07/2012 19:02, Simon Peter Nicholls a ?crit : It's inter-process by design. I have a small single instance C++ program that I'm porting to Haskell. Once the first instance launched is up and running, subsequent launches send their command line params through to the single instance (file names). Similar to when a media player queues files in a play list. The most recent extra clue I have is that if I wrap the SendMessage function with my own C FFI version, my C function can both re-cast and output the CWString I have sent, and can successfully invoke the real SendMessage by overriding the CWString with a newly created Lblah string. It's just a shame it can't use the original! My next session will involve poking around at the two strings to learn why they are treated differently. On Wed, Jul 18, 2012 at 6:33 PM, Sylvain HENRY hsy...@gmail.com wrote: Are you sending the message to a window of the same process? -Sylvain Le 18/07/2012 18:28, Simon Peter Nicholls a ?crit : I've tried that without joy. Have reposted over at Haskell cafe, as per Brent's advice. Thanks to both of you. On Wed, Jul 18, 2012 at 5:56 PM, Sylvain HENRY hsy...@gmail.com wrote: Hi, [As I've just registered to the list, I don't have the original message. That's why I answer to Brent insted of Simon] By using withCWString, your CWString may be freed before the message is sent. Use newCWString instead and free in your receiving code. Cheers Sylvain Le 18/07/2012 17:47, Brent Yorgey a ?crit : Hi, Just a meta-comment: this doesn't seem like a beginner question to me. =) Perhaps someone on this list will know the answer (and there's nothing wrong with asking), but for such a specific question you may have better luck posting to haskell-cafe or StackOverflow. -Brent On Wed, Jul 18, 2012 at 03:14:46PM +0200, Simon Peter Nicholls wrote: I'm new to Haskell, and have had some good success with FFI so far, but using Win32's sendMessage to send a pointer in LPARAM or WPARAM is resulting in access violations at the other end. Is there some issue with my pointer conversions? Am I hitting some restriction, or missing some compiler options? It's driving me pretty crazy, after a very nice start to using Haskell. Some sending code: Foreign.C.String.withCWString frustrator $ \s - do let wParam = System.Win32.Types.castPtrToUINT s :: System.Win32.Types.WPARAM Graphics.Win32.sendMessage wnd Graphics.Win32.wM_APP wParam 0 wndProc receiving code: | wmsg == Graphics.Win32.wM_APP = do s - peekCWString $ System.Win32.Types.castUINTToPtr wParam putStrLn s return 0 The string will not be seen. Some extra notes: I can get wndProc messages and integral data generally. The pointer values match textually at both ends when shown
Beginners Digest, Vol 49, Issue 23
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Where do you put your tests? (damodar kulkarni) 2. automatically clean up Haskell code? (Christopher Howard) 3. Re: automatically clean up Haskell code? (Karol Samborski) -- Message: 1 Date: Thu, 19 Jul 2012 18:57:10 +0530 From: damodar kulkarni kdamodar2...@gmail.com Subject: Re: [Haskell-beginners] Where do you put your tests? To: Lorenzo Bolla lbo...@gmail.com Cc: beginners@haskell.org Message-ID: CAD5HsyoxG8JD9_002nuTUbA=3Q3AOJFE3HTVkF7B4Z_2Q=+d...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Good because library dependencies are reduced, but bad because tests are somewhat disconnected from the functions they are testing. AFAIK, it's a good engineering practice to separate the tests from the code they are supposed to test. Code management issues will be there, but those can be taken care with the help of cabal like tool. That way, a person who wants to test will use the test-files and the one who doesn't want will be spared the trouble of separating tests from the intended function code. Regards, Damodar On Thu, Jul 19, 2012 at 1:46 PM, Lorenzo Bolla lbo...@gmail.com wrote: Hi all, I'm writing some library code and I have hunit-tests and quickcheck-tests. I'm facing the problem of where to put these tests. These are the options I can think of: - Put the tests for a function in the same file where the function is defined. This is good because tests are close to the code being tested and work as a sort of documentation for it. But it's bad because the file requires HUnit, QuickCheck, Test.Framework, etc. to compile. - Same as above, but use some sort of preprocessing flag to ignore the Test suite when compiling the library (hence no dependencies on test libraries), but leave the code in place. No dependencies, but ugly. - Put the tests in completely separate files. Good because library dependencies are reduced, but bad because tests are somewhat disconnected from the functions they are testing. What do you expert suggest? How should I organize my test suites? (The same conundrum applies to benchmarking code.) Thanks, Lorenzo ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120719/4058cde5/attachment-0001.htm -- Message: 2 Date: Thu, 19 Jul 2012 18:19:36 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] automatically clean up Haskell code? To: Haskell Beginners beginners@haskell.org Message-ID: 5008c038.5000...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 Is there a program that can automatically clean up your Haskell code? That is, shrink to 80 columns, make tidy indentation, remove unnecessary whitespace, and all that sort of stuff...? -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 554 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120719/2ec3679a/attachment-0001.pgp -- Message: 3 Date: Fri, 20 Jul 2012 09:24:09 +0200 From: Karol Samborski edv.ka...@gmail.com Subject: Re: [Haskell-beginners] automatically clean up Haskell code? To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: cace2dtuges_j94phmjfoa0yda9frht03q27ophogcudatmt...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 2012/7/20 Christopher Howard christopher.how...@frigidcode.com: Is there a program that can automatically clean up your Haskell code? That is, shrink to 80 columns, make tidy indentation, remove unnecessary whitespace, and all that sort of stuff...? Vim, emacs? Best, Regards -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 49, Issue 23 *
Beginners Digest, Vol 49, Issue 24
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: automatically clean up Haskell code? (Brent Yorgey) 2. Re: automatically clean up Haskell code? (Christian Maeder) -- Message: 1 Date: Fri, 20 Jul 2012 07:09:12 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] automatically clean up Haskell code? To: beginners@haskell.org Message-ID: 20120720110912.ga32...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Thu, Jul 19, 2012 at 06:19:36PM -0800, Christopher Howard wrote: Is there a program that can automatically clean up your Haskell code? That is, shrink to 80 columns, make tidy indentation, remove unnecessary whitespace, and all that sort of stuff...? Try http://hackage.haskell.org/package/stylish%2Dhaskell . -Brent -- Message: 2 Date: Fri, 20 Jul 2012 13:54:36 +0200 From: Christian Maeder christian.mae...@dfki.de Subject: Re: [Haskell-beginners] automatically clean up Haskell code? To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: 500946fc.7060...@dfki.de Content-Type: text/plain; charset=ISO-8859-1; format=flowed You may want to try out (and complain afterwards) scan -i file.hs http://hackage.haskell.org/package/scan scan does not break your lines that are longer than 80 chars, though, but it reports those. C. Am 20.07.2012 04:19, schrieb Christopher Howard: Is there a program that can automatically clean up your Haskell code? That is, shrink to 80 columns, make tidy indentation, remove unnecessary whitespace, and all that sort of stuff...? -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 49, Issue 24 *
Beginners Digest, Vol 49, Issue 25
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Where do you put your tests? (Michael Orlitzky) 2. Re: Where do you put your tests? (Magnus Therning) 3. Re: Where do you put your tests? (Brent Yorgey) 4. Re: Where do you put your tests? (Michael Orlitzky) 5. simple sound playback (Gnu/Linux) (Christopher Howard) 6. Re: Where do you put your tests? (Magnus Therning) -- Message: 1 Date: Sat, 21 Jul 2012 13:50:46 -0400 From: Michael Orlitzky mich...@orlitzky.com Subject: Re: [Haskell-beginners] Where do you put your tests? To: beginners@haskell.org Message-ID: 500aebf6.3020...@orlitzky.com Content-Type: text/plain; charset=ISO-8859-1 On 07/19/2012 09:27 AM, damodar kulkarni wrote: Good because library dependencies are reduced, but bad because tests are somewhat disconnected from the functions they are testing. AFAIK, it's a good engineering practice to separate the tests from the code they are supposed to test. Code management issues will be there, but those can be taken care with the help of cabal like tool. That way, a person who wants to test will use the test-files and the one who doesn't want will be spared the trouble of separating tests from the intended function code. This is the solution I'd prefer, but I quickly ran into a problem: if I want to test internal (non-exported) functions, the tests need to be in the same module as the code. Is there a way around this? (For now, I just put the code in the same file and depend on the test libs.) -- Message: 2 Date: Sat, 21 Jul 2012 20:04:35 +0200 From: Magnus Therning mag...@therning.org Subject: Re: [Haskell-beginners] Where do you put your tests? To: Michael Orlitzky mich...@orlitzky.com Cc: beginners@haskell.org Message-ID: CAAExw5sQ0DiH19T-R=ZxLfXauz9jdSnz+XFsmR=oseg7qjb...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Sat, Jul 21, 2012 at 7:50 PM, Michael Orlitzky mich...@orlitzky.com wrote: On 07/19/2012 09:27 AM, damodar kulkarni wrote: Good because library dependencies are reduced, but bad because tests are somewhat disconnected from the functions they are testing. AFAIK, it's a good engineering practice to separate the tests from the code they are supposed to test. Code management issues will be there, but those can be taken care with the help of cabal like tool. That way, a person who wants to test will use the test-files and the one who doesn't want will be spared the trouble of separating tests from the intended function code. This is the solution I'd prefer, but I quickly ran into a problem: if I want to test internal (non-exported) functions, the tests need to be in the same module as the code. Is there a way around this? (For now, I just put the code in the same file and depend on the test libs.) A common issue. I, and some others I've seen, have a FooInternal module exporting *everything* for the tests, and a Foo module exporting only the public API. /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: mag...@therning.org jabber: mag...@therning.org twitter: magthe http://therning.org/magnus -- Message: 3 Date: Sat, 21 Jul 2012 14:12:21 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Where do you put your tests? To: beginners@haskell.org Message-ID: 20120721181220.ga18...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Sat, Jul 21, 2012 at 08:04:35PM +0200, Magnus Therning wrote: On Sat, Jul 21, 2012 at 7:50 PM, Michael Orlitzky mich...@orlitzky.com wrote: On 07/19/2012 09:27 AM, damodar kulkarni wrote: Good because library dependencies are reduced, but bad because tests are somewhat disconnected from the functions they are testing. AFAIK, it's a good engineering practice to separate the tests from the code they are supposed to test. Code management issues will be there, but those can be taken care with the help of cabal like tool. That way, a person who wants to test will use the test-files and the one who doesn't want will be spared the trouble of separating tests from the intended function code. This is the solution I'd prefer, but I quickly ran into a problem: if I want to test internal (non-exported) functions, the tests need to be in the same module as the code. Is there a way around this? (For now, I just put the
Beginners Digest, Vol 49, Issue 26
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Pb with toggleActionNew (Pierre Michallet) 2. Re: Pb with toggleActionNew (Brandon Allbery) 3. Re: Pb with toggleActionNew (Nick Vanderweit) 4. Re: simple sound playback (Gnu/Linux) (Stephen Tetley) -- Message: 1 Date: Sun, 22 Jul 2012 16:46:56 +0200 From: Pierre Michallet p.michal...@free.fr Subject: [Haskell-beginners] Pb with toggleActionNew To: beginners haskell beginners@haskell.org Message-ID: 8F8862782F1248EF96C8E6DFD996293F@medione9995867 Content-Type: text/plain; charset=iso-8859-1 I am trying to become acquainted with both haskell and Gtk thru the writing of small pieces of code exercising some Gtk functions. Having had problems with the ToggleEntry function (unable to get the checked/non checked status - refer to chapter 7.2 of the Gtk2HS tutorial) I have tried to understand the toggleAction thing. So I have written this : import Graphics.UI.Gtk.ActionMenuToolbar.ToggleAction ... togls::[ToggleAction] togls = let stone = toggleActionNew STON Stones number Nothing Nothing (myTog stone) deste = toggleActionNew DEST Destination Nothing Nothing (myTog deste) state = toggleActionNew STAT Board status Nothing Nothing (myTog state) in [stone,deste,state] myTog::ToggleAction-IO() myTog ta = putStrLn (The name of the action is ++ (toggleActionName ta)) The compiler is not happy with this and sends back the following: --- The function 'toggleActionNew' is applied to five arguments but its type 'String -String -Maybe String - Maybe stockId -IO ToggleAction has only four. --- To me, stone has 4 parameters (STON, Stones number, Nothing,Nothing) and a result (myTog stone) as in the definition given by the compiler. I am using ghc-7.0.3 gthk+-bundle_2.16.2-20090601_win32 gtk-0.12.3.1 documentation I am certainly missing something obvious to everybody but I could not solve it , so I would appreciate any help on this topic. Thanks in advance p.michal...@free.fr -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120722/cb072eb2/attachment-0001.htm -- Message: 2 Date: Sun, 22 Jul 2012 11:22:11 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] Pb with toggleActionNew To: Pierre Michallet p.michal...@free.fr Cc: beginners haskell beginners@haskell.org Message-ID: CAKFCL4Xd+8GJJu=luiwqhmbvueydonk0oquxxb7ee759jue...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Sun, Jul 22, 2012 at 10:46 AM, Pierre Michallet p.michal...@free.frwrote: ** To me, stone has 4 parameters (STON, Stones number, Nothing,Nothing) and a result (myTog stone) as in the definition given by the compiler. Yes. So why are you trying to provide the result that it's supposed to produce? -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120722/ce35e86e/attachment-0001.htm -- Message: 3 Date: Sun, 22 Jul 2012 15:13:30 -0600 From: Nick Vanderweit nick.vanderw...@gmail.com Subject: Re: [Haskell-beginners] Pb with toggleActionNew To: beginners@haskell.org Message-ID: 6369472.JAMQu0YQAV@euler Content-Type: text/plain; charset=us-ascii Besides the fact that you are trying to pass the result of toggleActionNew as an argument, you're going to end up with problems regarding the type signature of togls when you try to invoke toggleActionNew, whose type
Beginners Digest, Vol 49, Issue 30
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. List syntax (Stayvoid) 2. Re: List syntax (Brandon Allbery) 3. Re: List syntax (Stayvoid) 4. Re: List syntax (Lyndon Maydwell) 5. Re: List syntax (Christian Maeder) 6. cabal / haddock: view source with API (Christopher Howard) -- Message: 1 Date: Fri, 27 Jul 2012 17:27:25 +0400 From: Stayvoid stayv...@gmail.com Subject: [Haskell-beginners] List syntax To: beginners@haskell.org Message-ID: CAK5fS_Hat3Or=jzw6qe3hwtvudyombn_wp0egkne81qkvvw...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi, Why can't we do this: [LT..GT]? The following works: ['a'..'e'] ['a' .. 'e'] [LT .. GT] Cheers -- Message: 2 Date: Fri, 27 Jul 2012 10:49:58 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] List syntax To: Stayvoid stayv...@gmail.com Cc: beginners@haskell.org Message-ID: CAKFCL4W=1ue-ovo6ozhzpvjz3cuxxvte5xf-t9ozwkw5-1h...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Fri, Jul 27, 2012 at 9:27 AM, Stayvoid stayv...@gmail.com wrote: Why can't we do this: [LT..GT]? Because LT.. is the operator (.) in the module LT, and is unexpected there. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120727/62630d12/attachment-0001.htm -- Message: 3 Date: Fri, 27 Jul 2012 18:53:47 +0400 From: Stayvoid stayv...@gmail.com Subject: Re: [Haskell-beginners] List syntax To: beginners@haskell.org Message-ID: cak5fs_frd398fbsk3jfkwzmve0xc78yzxi1fn06m93zy-n3...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Thanks. -- Message: 4 Date: Fri, 27 Jul 2012 23:01:20 +0800 From: Lyndon Maydwell maydw...@gmail.com Subject: Re: [Haskell-beginners] List syntax To: Stayvoid stayv...@gmail.com, Beginners Haskell beginners@haskell.org Message-ID: cam5qztxbdej4q8jpqkaxtzm6-ptxcznnd0033wrvcp2feqj...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Fri, Jul 27, 2012 at 10:52 PM, Stayvoid stayv...@gmail.com wrote: Thanks. P.S. I think that you should send your answer to the list to show the others that this issue is solved. Ah, I thought I replied to all. Well, here is my reply for the record :-) Here's what I'm describing in a GHCi session: ? [LT..GT] interactive:2:2: Failed to load interface for `LT' Use -v to see a list of the files searched for. interactive:2:2: A section must be enclosed in parentheses thus: (LT.. GT) I'm assuming that this was the error that you encountered when you tried to use the syntax [LT..GT]. In my example I used a renamed module, but this also makes sense for a module imported the usual way. I renamed the module so you could see directly how an ambiguity could occur for 'LT'. If you import a module you can rename it by using the 'as' keyword, in this case, 'LT'. There is now an ambiguity between 'LT' = less than and 'LT' = Data.List. ? import qualified Data.List as LT ? :i LT.map map :: (a - b) - [a] - [b] -- Defined in `GHC.Base' Here is a demonstration of the renamed module in action. ? :i LT.. Top level: Failed to load interface for `LT' Use -v to see a list of the files searched for. And here is what I think is causing your error to be thrown - The symbol '.' is being searched for in module LT in the same manner that 'map' was in the previous example, now given that there is no LT module, it is failing. This ambiguity might seem annoying, but it's not too bad since you can just put some spaces in to resolve it. -- Message: 5 Date: Fri, 27 Jul 2012 17:52:06 +0200 From: Christian Maeder christian.mae...@dfki.de Subject: Re: [Haskell-beginners] List syntax To: Lyndon Maydwell maydw...@gmail.com Cc: Beginners Haskell beginners@haskell.org Message-ID: 5012b926.1020...@dfki.de Content-Type: text/plain; charset=UTF-8; format=flowed In fact there is no ambiguity (but ghc does not bother to resolve this). No legal expression can start with a (qualified) symbol like ., so since you used square brackets rather than round ones (to make a section) the resolution could be unique (by accepting an
Beginners Digest, Vol 49, Issue 32
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Here's why functions should return functions (Ertugrul S?ylemez) -- Message: 1 Date: Mon, 30 Jul 2012 06:38:40 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] Here's why functions should return functions To: beginners@haskell.org Message-ID: 20120730063840.68d14...@tritium.streitmacht.eu Content-Type: text/plain; charset=utf-8 Jay Sulzberger j...@panix.com wrote: There is, in most sub-systems of mathematics, whether like recent type theory or not, a general function, let us call it mcf which in Scheme notation may be defined by executing (define mcf (lambda (a) (lambda (x) a))) Now in Haskell I know that one, perhaps the, parallel definition must result in a polymorphic function. First let's ensure that we are talking about the same function. I'm reading mcf as make constant function. From what I read the Haskell equivalent would be this function: const a _ = a It may make it not fully polymorphic, but if you don't provide a type signature, then the following fully polymorphic type will be inferred: const :: a - b - a What is this definition? Well, this is the constant function, though with slightly unusual (but sensible) semantics for Scheme. Because Scheme syntax requires explicit currying the name make constant function would also be sensible. It is because of the lack of side effects that we call the function simply 'const' in Haskell. Otherwise most functions would be prefixed with make. What implicit constraints are on a? None. Does lazy vs eager come in here? Yes. Even though you have written a curried version of 'const' there, Scheme is still a strict language, which means that the result of the inner lambda will depend on its argument 'x'. This means: -- Haskell: const a ? = a -- in other words: loop = loop -- an infinite loop const a loop = a ; Scheme: ((mcf a) ?) = ? (define (loop) (loop)) ; an infinite loop ((mcf a) (loop)) = (loop) This is the semantic difference. To relate this to lazy vs. eager it's important to understand how a nonstrict language like Haskell is usually evaluated: Lazy evaluation will defer the evaluation of the inner lambda's argument (which is an unnamed '_' here) until it is required. Since it is never required it is never evaluated and the unevaluated thunk is garbage-collected immediately, unless it is used elsewhere. A strict language like Scheme is usually evaluated eagerly. This means that the inner lambda is not entered, until the argument is fully evaluated. Are there options to ghc which might modify how Haskell handles the definition? There are optimization flags, which could change the performance of the definition, but a proper Haskell compiler like GHC must ensure that semantics are not changed. Of course, my questions are too many and I hope just for some indications of the first things a beginner should study. No worries. I'm happy to help. =) Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120730/adf81b88/attachment-0001.pgp -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 49, Issue 32 *
Beginners Digest, Vol 49, Issue 35
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Today's Topics:
1. Re: XmlPickler on ADT (Tim Perry)
--
Message: 1
Date: Tue, 31 Jul 2012 13:14:49 -0700
From: Tim Perry tim.v...@gmail.com
Subject: Re: [Haskell-beginners] XmlPickler on ADT
To: Haskell Beginners beginners@haskell.org
Message-ID:
cafvgasvbz1cnezt_fvrcjjlw75o56yjde-sfxy5dafx-h5h...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
I found the error. I used Renewable as the name of the XML element tag
when it should have been Renewables with a trailing s. Oops. Sorry for
the spam -- Tim
On Tue, Jul 31, 2012 at 10:55 AM, Tim Perry tim.v...@gmail.com wrote:
Hi everyone,
I'm trying to learn to write XmlPicklers. I've been trying to follow the
tutorial on the HaskelWiki, but it doesn't quite cover an issue I've run
into.
http://www.haskell.org/haskellwiki/HXT/Conversion_of_Haskell_data_from/to_XML
I have a ADTs like so:
data Plant = Plant
{ renewables :: [Renewable]
, rewewableMonthly :: [RenewableMonthly]
, waterHeating :: [WaterHeating]
, hvac :: [HVAC]
} deriving (Read, Show, Eq)
data Renewable = Renewable
{ dcRating :: Double -- kW
, annualTDV :: Double -- CA Energy Comm. TDV
} deriving (Read, Show, Eq)
data RenewableMonthly = RenewableMonthly
{ month :: Int
, cost :: Double
, demand :: Double
, energy :: Double
} deriving (Read, Show, Eq)
data WaterHeating = WaterHeating
{ whName :: String -- name for reference purposes.
, whQuantity :: Int
...
data HVAC = HVAC
{ slaStatus :: String -- Specific leakage area
construction type.
, newCFM50 :: Double -- New building leakage in cubic
feet per minute.
, existCFM50 :: Double
I want to use an XmlPickler to read and write this. The XML looks like
this:
Plant
Renewables DCRating=8.4 AnnualTDV=0 /
RenewableMonthly Month=1 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=2 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=3 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=4 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=5 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=6 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=7 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=8 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=9 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=10 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=11 Cost=0 Demand=0 Energy=0 /
RenewableMonthly Month=12 Cost=0 Demand=0 Energy=0 /
WaterHeating Name=Daikin Altherma HP Quantity=1
ConstructionStatus=New EnergyFactor=2.344 SolarFraction=0
HVAC SLAStatus=New NewCFM50=0 ExistCFM50=0
NewSLA=4.900953674316 ExistSLA=4.9 DuctStatus=New
Zone ...
Running my code I get an error:
-- (1) readDocument: start processing document 1101_11-001 Walsh.xml --
(1) getXmlContents: content read and decoded for
file:///fairoaks1/all_proj/1101%20PGE%20CAHP%2011-12/CRM/EProDataExtractPlanning/XML%20samples/1101_11-001%20Walsh.xml
-- (1) getXmlContents' -- (1) readDocument: 1101_11-001 Walsh.xml (mime
type: text/xml ) will be processed -- (1) readDocument: 1101_11-001
Walsh.xml processed
fatal error: document unpickling failed
xpCheckEmptyContents: unprocessed XML content detected context: element
Plant contents:
Is it possible to write an XmlPickler for this? Do I need to make
Renewable, RenewableMonthly, WaterHeating, and HVAC all the same type with
4 constructors and use xpAlt? Ideas?
Thanks,
Tim
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Beginners Digest, Vol 50, Issue 3
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Resources to learn functional programming (Hilco Wijbenga) 2. Re: Resources to learn functional programming (Dudley Brooks) 3. Re: Resources to learn functional programming (David Hinkes) 4. Re: Resources to learn functional programming (Lorcan McDonald) 5. Re: Resources to learn functional programming (Arthur Clune) -- Message: 1 Date: Wed, 1 Aug 2012 15:09:09 -0700 From: Hilco Wijbenga hilco.wijbe...@gmail.com Subject: Re: [Haskell-beginners] Resources to learn functional programming To: Tim Perry tim.v...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAE1pOi1fSTcdNEgLs2-c=+kvkiyaweyvm+0jvptdww6b1sm...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On 1 August 2012 14:23, Tim Perry tim.v...@gmail.com wrote: I think that you should work your way through Real World Haskell which is available free online. I thought it was worth-while enough that I bought the book and I regularly refer to it. http://book.realworldhaskell.org/ Learn you a Haskell for Great Good is also a worth-while book. http://learnyouahaskell.com/ A very big +1 for this one. LYAHFGG really made it click for me. RWH is an excellent book too but more for subsequent reading (at least for me). (I recently bought both LYAHFGG and RWH. The decision to buy was made much easier by the fact that I was able to read them online first.) -- Message: 2 Date: Wed, 01 Aug 2012 15:14:54 -0700 From: Dudley Brooks dbro...@runforyourlife.org Subject: Re: [Haskell-beginners] Resources to learn functional programming To: Haskell Beginners beginners@haskell.org Message-ID: 5019aa5e.4070...@runforyourlife.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 8/1/12 2:23 PM, Tim Perry wrote: I think that you should work your way through Real World Haskell which is available free online. I thought it was worth-while enough that I bought the book and I regularly refer to it. http://book.realworldhaskell.org/ Learn you a Haskell for Great Good is also a worth-while book. http://learnyouahaskell.com/ The Haskell wikibook is also good, available online as HTML or PDF: http://en.wikibooks.org/wiki/Haskell Personally, I found that Learn You a Haskell started to get obscure at about the chapter on monads, just where the most clarity is needed, and that the wikibook was clearer. But different strokes for different folks. (I haven't looked at that section of Real-World Haskell yet.) -- Dudley -- Message: 3 Date: Wed, 1 Aug 2012 15:15:01 -0700 From: David Hinkes david.hin...@gmail.com Subject: Re: [Haskell-beginners] Resources to learn functional programming To: Hilco Wijbenga hilco.wijbe...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CA+_CxFOgUNBuN6AwmE4Gvw65fkvtkaN8iLmYD4wa=cugsrp...@mail.gmail.com Content-Type: text/plain; charset=utf-8 And LYAHFGG is nice on the eyes. On Wed, Aug 1, 2012 at 3:09 PM, Hilco Wijbenga hilco.wijbe...@gmail.comwrote: On 1 August 2012 14:23, Tim Perry tim.v...@gmail.com wrote: I think that you should work your way through Real World Haskell which is available free online. I thought it was worth-while enough that I bought the book and I regularly refer to it. http://book.realworldhaskell.org/ Learn you a Haskell for Great Good is also a worth-while book. http://learnyouahaskell.com/ A very big +1 for this one. LYAHFGG really made it click for me. RWH is an excellent book too but more for subsequent reading (at least for me). (I recently bought both LYAHFGG and RWH. The decision to buy was made much easier by the fact that I was able to read them online first.) ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- David Hinkes -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120801/224ac63b/attachment-0001.htm -- Message: 4 Date: Wed, 1 Aug 2012 23:15:01 +0100 From: Lorcan McDonald lor...@lorcanmcdonald.com Subject: Re: [Haskell-beginners] Resources to learn functional programming To: David Hinkes david.hin...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID:
Beginners Digest, Vol 50, Issue 4
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Resources to learn functional programming (Patrick Redmond) 2. Re: Resources to learn functional programming (Homero Cardoso de Almeida) 3. Re: Resources to learn functional programming (Alexander Bernauer) 4. vector indexing time (Ivan Vyalov) 5. Re: vector indexing time (Alexander Dunlap) 6. Re: vector indexing time (Nick Vanderweit) -- Message: 1 Date: Thu, 2 Aug 2012 06:30:26 -0400 From: Patrick Redmond plredm...@gmail.com Subject: Re: [Haskell-beginners] Resources to learn functional programming To: Haskell Beginners beginners@haskell.org Message-ID: cahuea4h4lav2gcrnw_uhr43lqbqksuajfyowyhfczt8mizm...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Although many resources have been mentioned here, I'd like to recommend How To Design Programs, http://www.htdp.org/, which approaches functional programming from a Scheme (Racket) perspective. This book is how I learned functional programming and developed an interest in Haskell. In HTDP, higher order functions aren't introduced until you've been taught how to write similar code without them. Then you learn that your code can be abbreviated using things like map, foldl, foldr, ormap, andmap, etc. The book moves into more complicated uses of functions-as-data near the end. Hope you find it useful, Patrick On Thu, Aug 2, 2012 at 4:03 AM, Arthur Clune art...@clune.org wrote: In a similar vein, I highly recommend Higher Order Perl by Mark-Jason Dominus. It presents most of these concepts in a more familiar setting. Don't worry if you don't know perl, if you know C++, you'll know enough to follow the book. Arthur -- Arthur Clune art...@clune.org ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 2 Date: Thu, 2 Aug 2012 10:54:16 -0300 From: Homero Cardoso de Almeida homero...@gmail.com Subject: Re: [Haskell-beginners] Resources to learn functional programming To: Patrick Redmond plredm...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAPv0Zwop0eUZj999E2uZQiyTN3VN3aqJEWWMNZKQHP7ty=n...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Thanks for all the suggestions. I was learning Haskell through LYAHFGG, and that's when I got the problem with Higher Order functions. I'll take a look at all the resources posted. Thanks again, Homero Cardoso de Almeida On Thu, Aug 2, 2012 at 7:30 AM, Patrick Redmond plredm...@gmail.com wrote: Although many resources have been mentioned here, I'd like to recommend How To Design Programs, http://www.htdp.org/, which approaches functional programming from a Scheme (Racket) perspective. This book is how I learned functional programming and developed an interest in Haskell. In HTDP, higher order functions aren't introduced until you've been taught how to write similar code without them. Then you learn that your code can be abbreviated using things like map, foldl, foldr, ormap, andmap, etc. The book moves into more complicated uses of functions-as-data near the end. Hope you find it useful, Patrick On Thu, Aug 2, 2012 at 4:03 AM, Arthur Clune art...@clune.org wrote: In a similar vein, I highly recommend Higher Order Perl by Mark-Jason Dominus. It presents most of these concepts in a more familiar setting. Don't worry if you don't know perl, if you know C++, you'll know enough to follow the book. Arthur -- Arthur Clune art...@clune.org ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120802/b7a6a76f/attachment-0001.htm -- Message: 3 Date: Thu, 2 Aug 2012 16:19:01 +0200 From: Alexander Bernauer alex-hask...@copton.net Subject: Re: [Haskell-beginners] Resources to learn functional programming To: beginners@haskell.org Message-ID: 20120802141901.GB2608@apus Content-Type: text/plain; charset=us-ascii On Wed, Aug 01, 2012 at 05:53:36PM -0300, Homero
Beginners Digest, Vol 50, Issue 7
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Using a concept from Category Theory to enable you to come back home after your function has taken you somewhere (Brent Yorgey) 2. Re: Using a concept from Category Theory to enable you to come back home after your function has taken you somewhere (Miguel Negrao) 3. Re: DPH installation and LLVM (Erik de Castro Lopo) -- Message: 1 Date: Sun, 5 Aug 2012 08:37:30 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Using a concept from Category Theory to enable you to come back home after your function has taken you somewhere To: beginners@haskell.org Message-ID: 20120805123730.ga23...@seas.upenn.edu Content-Type: text/plain; charset=iso-8859-1 On Sat, Aug 04, 2012 at 05:59:59PM +, Costello, Roger L. wrote: How to automatically get the inverse of a Haskell function? That's a great question. I don't know the answer to that. Anyone else have an idea? It is not possible in general... but on the other hand you can use parametricity to pull some cool tricks. See Janis Voigtl?nder's paper from 2009, Bidirectionalization for free! (http://www.iai.uni-bonn.de/~jv/popl09-2.pdf) which is a fun read. You can even play with an implementation of it here: http://www-ps.iai.uni-bonn.de/cgi-bin/bff.cgi -Brent -- Message: 2 Date: Sun, 5 Aug 2012 14:05:58 +0100 From: Miguel Negrao miguel.negrao-li...@friendlyvirus.org Subject: Re: [Haskell-beginners] Using a concept from Category Theory to enable you to come back home after your function has taken you somewhere To: beginners@haskell.org Message-ID: fc3d31e0-d380-4485-a5ac-96b8f747c...@friendlyvirus.org Content-Type: text/plain; charset=windows-1252 Hi Roger, A 04/08/2012, ?s 18:59, Costello, Roger L. escreveu: Hi Miguel, First note that I am very much a beginner at Category Theory. I am just sharing what I learn. Yes I understand that, but what I was trying to say is that I don?t think that this is much related with category theory. How do you know that a Haskell function is injective? I don't think it's possible to write a function which checks if another function is injective or not . A function is injective if each input value (domain) yields a different output value (codomain). So if the set of inputs is finite, then it should be possible to write a function that loops over each input value and checks that its output is distinct from all other outputs. Yes, but very few functions have finite domains, and if they do and it?s big it would take a long time to test it. That is not a technique that can be used in practice I think. Brent wrote: It is not possible in general... but on the other hand you can use parametricity to pull some cool tricks. See Janis Voigtl?nder's paper from 2009, Bidirectionalization for free! (http://www.iai.uni-bonn.de/~jv/popl09-2.pdf) which is a fun read. You can even play with an implementation of it here: http://www-ps.iai.uni-bonn.de/cgi-bin/bff.cgi -Brent Yes, I think that was the paper I had seen. Interesting stuff. best, Miguel Negr?o -- Message: 3 Date: Mon, 6 Aug 2012 18:55:31 +1000 From: Erik de Castro Lopo mle...@mega-nerd.com Subject: Re: [Haskell-beginners] DPH installation and LLVM To: beginners@haskell.org Message-ID: 20120806185531.c89910a9cacd7e06f6341...@mega-nerd.com Content-Type: text/plain; charset=UTF-8 listig...@gmail.com wrote: Since I haven't gotten any further answers I'm trying my luck again? Does anyone have an idea how I can get the llvm backend to work? My configuration is: Mac OS X 10.7.4 XCode 4.3.3 (with Command Line Tools installed) Haskell Platform 2012.2.0.0 32 bit llvm (via Homebrew) DPH is not really a beginners topic. Maybe you should try the haskell-cafe list. Erik -- -- Erik de Castro Lopo http://www.mega-nerd.com/ -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 50, Issue 7
Beginners Digest, Vol 50, Issue 11
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: what is a qualified type? (Heinrich Apfelmus) 2. cabal errors.. (Gregory Guthrie) 3. Re: cabal errors.. (Stephen Tetley) -- Message: 1 Date: Fri, 10 Aug 2012 13:29:47 +0200 From: Heinrich Apfelmus apfel...@quantentunnel.de Subject: Re: [Haskell-beginners] what is a qualified type? To: beginners@haskell.org Message-ID: k02rba$ode$1...@dough.gmane.org Content-Type: text/plain; charset=UTF-8; format=flowed Christopher Howard wrote: In short, what is a qualified type and how is it used? (Any examples would be appreciated.) I feel somewhat embarrassed asking, as I used to know. I dropped Haskell a while ago and am just now picking it up again, and unfortunately I have forgotten many concepts. If someone could point me to the appropriate tutorial that might be enough. For some reason, all my StartPage searches are only bringing me to documents that assume I already understand qualified types, or to books I can't afford to buy. This is a type: [a] - a This is a qualified type: Num a = [a] - a You can say that qualified types are types that include constraints via the = symbol. In Haskell, you will mostly see type class constraints, but there are other possibilities as well. They are all grouped together in the notion of qualified types. http://www.haskell.org/haskellwiki/Research_papers/Type_systems#Qualified_types As a practicing Haskell programmer, you don't actually need to know how the theory of qualified types works. The only thing you need to be aware of the expression ambiguous constraint, because that's an occasional error message in GHC. Here an example: Show a = Int - Bool -- ambiguous constraint Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com -- Message: 2 Date: Fri, 10 Aug 2012 21:14:18 -0500 From: Gregory Guthrie guth...@mum.edu Subject: [Haskell-beginners] cabal errors.. To: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01e265dd1...@mail.cs.mum.edu Content-Type: text/plain; charset=us-ascii I am (again) running into cabal install issues; which have been all too common for me. In this case as an example, I tried this: C:\Users\haskellCabal install buildwrapper . buildwrapper-0.6.0 depends on regex-tdfa-1.1.8 which failed to install. regex-tdfa-1.1.8 failed during the building phase. The exception was: ExitFailure 1 So I tried this: C:\Users\haskellcabal install regex-tdfa Resolving dependencies... In order, the following would be installed: regex-base-0.93.2 (reinstall) changes: array-0.3.0.2 - 0.4.0.0, base-4.3.1.0 - 4.5.0.0, bytestring-0.9.1.10 - 0.9.2.1, containers-0.4.0.0 - 0.4.2.1, mtl-2.0.1.0 - 2.1.2 regex-tdfa-1.1.8 (new package) cabal: The following packages are likely to be broken by the reinstalls: regex-posix-0.95.1 regex-compat-0.95.1 haskell-platform-2011.3.0.0 regex-posix-0.94.4 regex-compat-0.93.1 haskell-platform-2011.2.0.1 regex-posix-0.95.1 regex-compat-0.95.1 haskell-platform-2012.2.0.0 Use --force-reinstalls if you want to install anyway. So what to do? Last time I got into a situation like this I tried to start-over with cabal, remove all local cache and rebuild the library. From a suggestion in SO; delete the ~/ghc ~/cabal files and restart cabal, by a cabal install cabal-install. Didn't help much, still stuck. Any hints? I find that library issues like this with cabal are the biggest time-soak I have with using Haskell, and I usually have to abandon attempts to try some new library for various examples. Ghc-pkg check lists lots of warnings, but all from haddock-html or haddock-interface; not sure what to make of that but I think it just means that somehow documentation was not installed for these packages. cabal -V cabal-install version 0.14.0 using version 1.14.0 of the Cabal library GHCi version 7.4.1 HaskellPlatform-2012.2.0.0 --- -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120810/31721615/attachment.htm -- Message: 3 Date: Sat, 11 Aug 2012 07:00:50 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] cabal errors.. To:
Beginners Digest, Vol 50, Issue 12
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cabal errors.. (Brandon Allbery) 2. Cabal error (Gregory Guthrie) -- Message: 1 Date: Sat, 11 Aug 2012 10:31:41 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] cabal errors.. To: Stephen Tetley stephen.tet...@gmail.com Cc: Gregory Guthrie guth...@mum.edu, beginners@haskell.org beginners@haskell.org Message-ID: CAKFCL4WZb7+LhgVqUFLmdTkdcnV=o6zort+6-buohzbk3rb...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Sat, Aug 11, 2012 at 2:00 AM, Stephen Tetley stephen.tet...@gmail.comwrote: From the cabal file accessible on Hackage it looks like you need to build regex-tfda with the build flag base4. cabal-install should be figuring that out for itself unless the versions of prerequisites are specified incorrectly. I don't uses cabal-install so can't say how to send it build flags --flags=flag1[,flag2,...] -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120811/ffef5489/attachment-0001.htm -- Message: 2 Date: Sat, 11 Aug 2012 23:37:16 -0500 From: Gregory Guthrie guth...@mum.edu Subject: [Haskell-beginners] Cabal error To: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01e265dd1...@mail.cs.mum.edu Content-Type: text/plain; charset=us-ascii I get the following Cabal install error: C:\Users\haskellcabal install buildwrapper Resolving dependencies... Configuring regex-tdfa-1.1.8... Warning: This package indirectly depends on multiple versions of the same package. This is highly likely to cause a compile failure. If true, doesn't this mean that the regex-tdfa package has misconfigured dependencies? --- -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120811/9822b44d/attachment-0001.htm -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 50, Issue 12 *
Beginners Digest, Vol 50, Issue 14
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cabal install errors (Gregory Guthrie) 2. Re: cabal install errors (Stephen Tetley) 3. Re: cabal install errors (Gregory Guthrie) 4. Re: cabal install errors (Stephen Tetley) 5. Re: cabal install errors (Henk-Jan van Tuyl) 6. Re: cabal install errors (Gregory Guthrie) 7. Re: cleanest way to unwrap a list? (Jack Henahan) 8. Re: cleanest way to unwrap a list? (Christopher Howard) 9. Re: cleanest way to unwrap a list? (Jack Henahan) -- Message: 1 Date: Mon, 13 Aug 2012 07:31:19 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] cabal install errors To: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01e265dd1...@mail.cs.mum.edu Content-Type: text/plain; charset=us-ascii I didn't get any concrete remedy for this, or its underlying cause. Does it mean that this package is incompatible with others currently installed, and I am supposed to make a choice to uninstall or break them by forcing this, or ...??? --- I tried this: C:\Users\haskellcabal install regex-tdfa Resolving dependencies... In order, the following would be installed: regex-base-0.93.2 (reinstall) changes: array-0.3.0.2 - 0.4.0.0, base-4.3.1.0 - 4.5.0.0, bytestring-0.9.1.10 - 0.9.2.1, containers-0.4.0.0 - 0.4.2.1, mtl-2.0.1.0 - 2.1.2 regex-tdfa-1.1.8 (new package) cabal: The following packages are likely to be broken by the reinstalls: regex-posix-0.95.1 regex-compat-0.95.1 haskell-platform-2011.3.0.0 regex-posix-0.94.4 regex-compat-0.93.1 haskell-platform-2011.2.0.1 regex-posix-0.95.1 regex-compat-0.95.1 haskell-platform-2012.2.0.0 Use --force-reinstalls if you want to install anyway. So what to do? cabal -V cabal-install version 0.14.0 using version 1.14.0 of the Cabal library GHCi version 7.4.1 HaskellPlatform-2012.2.0.0 --- -- Message: 2 Date: Mon, 13 Aug 2012 17:40:03 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org beginners@haskell.org Message-ID: cab2tprbwyfw5rtn-ja7ceibhgxxlzccvzsv8tex7o_xiz_5...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 The latest regex-tdfa is compatible with with the packages you have installed, but cabal-install evidently wants to update all of regex-tdfa's dependencies which thus breaks things. Presumably cabal-install has an option not to transitively update dependencies? As I don't use cabal-install I don't know it myself. -- Message: 3 Date: Mon, 13 Aug 2012 11:41:46 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] cabal install errors To: Stephen Tetley stephen.tet...@gmail.com Cc: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01e265dd1...@mail.cs.mum.edu Content-Type: text/plain; charset=us-ascii Wouldn't this indicate some errors in the cabal install setup with the package? So the solution is to get the package, and install directly? Thanks. --- Subject: Re: [Haskell-beginners] cabal install errors The latest regex-tdfa is compatible with with the packages you have installed, but cabal- install evidently wants to update all of regex-tdfa's dependencies which thus breaks things. Presumably cabal-install has an option not to transitively update dependencies? As I don't use cabal-install I don't know it myself. -- Message: 4 Date: Mon, 13 Aug 2012 18:38:24 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org beginners@haskell.org Message-ID: CAB2TPRBhViLhh-1Uk-iAQs67ioFT5++4+rLxax1WO+PqK3V=a...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 The .cabal file in regex-tdfa is pretty relaxed about version numbers, so I don't see see an error there. If it were me I'd install it form local with runhaskell Setup.hs configure; runhaskell Setup.hs build; runhaskell Setup.hs install -- Message: 5 Date: Mon,
Beginners Digest, Vol 50, Issue 15
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cabal install errors (Carlos J. G. Duarte) 2. Re: cabal install errors (Benjamin Edwards) 3. Re: cleanest way to unwrap a list? (Carlos J. G. Duarte) 4. Re: cleanest way to unwrap a list? (Tim Perry) 5. Re: cleanest way to unwrap a list? (Carlos J. G. Duarte) -- Message: 1 Date: Tue, 14 Aug 2012 11:54:35 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors To: beginners@haskell.org Message-ID: 502a2e6b.8070...@gmail.com Content-Type: text/plain; charset=us-ascii An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120814/5bc176de/attachment-0001.htm -- Message: 2 Date: Tue, 14 Aug 2012 13:08:49 +0100 From: Benjamin Edwards edwards.b...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: can6k4nj5oz2e994pv8qdn89c1emhpx5-a191f5ettzkqu8u...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I think one point bears repeating: cabal is a build system, really. It does a good enough job of that. It is a *terrible* package manager and using it as one I think is a classic mistake that the community needs to address. My two-penneth worth is this: Use cabal-dev, or hsenv, for *everything* and 99% of your woes will go away. The the only thing I do when getting haskell up and running is to get cabal-dev installed and it's dependencies in the cabal per user pkg store and then cabal-dev sandboxes for everything from then on. On Aug 14, 2012 11:57 AM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: On 08/13/12 22:19, Gregory Guthrie wrote: Thanks, I'll try that, but it looks like it could be a lot of maintenance and manual cleanup! I haven't knowingly done any manual upgrades of core packages, but I have done updates as asked by cabal when it thinks the database is getting old. I have had such pedestrian usage that I would not have expected to have goofed up the database! :-) Cabal seems to be more troublesome that other various *package managers* like apt, etc... Please see this: http://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-is-not-a-package-manager/ But yes, cabal or not, I agree that there should be a better system for managing haskell packages, like pip, gem or cpan... but that boils down to the problem that some has to do it, and people who are able to do it** are often too busy for that. ** and that doesn't include me, as I'm just starting to explore Haskell on my spare time. All in all, cabal suits me even with its idiosyncrasies. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120814/4fb0d351/attachment-0001.htm -- Message: 3 Date: Tue, 14 Aug 2012 19:05:56 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: Re: [Haskell-beginners] cleanest way to unwrap a list? To: beginners@haskell.org Message-ID: 502a9384.9090...@gmail.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed Ok, you all have been showing examples of running functions over elements. Add one, append value, and so on. This works well if there's one or more operations to apply indistinctly to a number of elements. Now, what if we just want to make a single operation to a single element? For example, let's say I have this square matrix [[1,2,3], [4,5,6], [7,8,9]] how can we increment the value 5 (position 2,2) *and* decrement the value 7 (position 3,1)? This is a made up example of course, I just want to see / learn if there's a way to apply a function to a specific subset of elements. On 08/14/12 00:06, Jack Henahan wrote: Equally, let map' = map . map map' (+1) . map (++[3]) $ [[1,2],[3,4]] -- [[2,3,4],[4,5,4]] And you can really keep stacking those up. I think this approach will be cleaner in the long run. For instance, let's start naming our parts. let list = [[1,2],[3,4]] let map' = map . map let addOne = map' (+1) let appendThree = map (++[3]) let reverseInner = map reverse So,
Beginners Digest, Vol 50, Issue 16
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cleanest way to unwrap a list? (Peter Hall) 2. Re: cleanest way to unwrap a list? (Nick Vanderweit) 3. Re: cabal install errors (damodar kulkarni) -- Message: 1 Date: Tue, 14 Aug 2012 23:59:46 +0100 From: Peter Hall peter.h...@memorphic.com Subject: Re: [Haskell-beginners] cleanest way to unwrap a list? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: CAA6hAk5ii7q2ptZPOU9ALm0U4X+Ofa_0UcqBPAuk9NKqwy8U=q...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 This is a bit more functional. The coordinates are the opposite way around, and it can probably be expressed a bit more concisely, but I'll leave that to you. This is the basic idea. -- maps over a list supplying also the 'index' mapi f = map (uncurry f) . zip [0..] -- maps over a list supplying also the coordinate pair mapii f a = mapi f' a where f' i x = mapi (curry f $ i) x m0 = [[1,2,3], [4,5,6], [7,8,9]] f (1,1) a = a+1 f (0,2) a = a-1 f (_,_) a = a mapii f m0 -- [[1,2,3],[4,6,6],[6,8,9]] Peter On 14 August 2012 22:50, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: I know it's doable. I was asking if there's a practical / elegant way to do it. I see a lot of Haskell elegance when the matter is defining math formulas, running functions over elements, and so on. But it seems most of that elegance goes away when the problem derails a bit. Now for my problem I come up with this: modify mat x y f = let (lrows, row, rrows) = getpart mat x (lcols, col, rcols) = getpart row y in lrows ++ [lcols ++ [f col] ++ rcols] ++ rrows where getpart xs x = let (ls, r:rs) = splitAt x xs in (ls, r, rs) m0 = [[1,2,3], [4,5,6], [7,8,9]] main = do print m0 let m1 = modify m0 1 1 succ let m2 = modify m1 2 0 pred print m2 Which is a bit awkward considering the ease it is done in other languages. On 08/14/12 19:35, Tim Perry wrote: There is a way. Please try to figure it out and if you fail post back with your code and we can help you from there. On Tue, Aug 14, 2012 at 11:05 AM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: Ok, you all have been showing examples of running functions over elements. Add one, append value, and so on. This works well if there's one or more operations to apply indistinctly to a number of elements. Now, what if we just want to make a single operation to a single element? For example, let's say I have this square matrix [[1,2,3], [4,5,6], [7,8,9]] how can we increment the value 5 (position 2,2) *and* decrement the value 7 (position 3,1)? This is a made up example of course, I just want to see / learn if there's a way to apply a function to a specific subset of elements. On 08/14/12 00:06, Jack Henahan wrote: Equally, let map' = map . map map' (+1) . map (++[3]) $ [[1,2],[3,4]] -- [[2,3,4],[4,5,4]] And you can really keep stacking those up. I think this approach will be cleaner in the long run. For instance, let's start naming our parts. let list = [[1,2],[3,4]] let map' = map . map let addOne = map' (+1) let appendThree = map (++[3]) let reverseInner = map reverse So, from here we can do the following: list -- [[1,2],[3,4]] -- the first example addOne list -- [[2,3],[4,5]] -- now the second example addOne . appendThree $ list -- [[2,3,4],[4,5,4]] -- now add one to all members of the list, append three to the list, reverse the inner lists, -- then add one to all members of the new list addOne . reverseInner . appendThree . addOne $ list -- [[4,4,3],[4,6,5]] Now how would you construct that as a list comprehension? With the method I've proposed, you need only use map to operate on the nested lists themselves and map' to operate on the elements of those lists. Jack Henahan jhena...@uvm.edu On Aug 13, 2012, at 6:41 PM, Christopher Howard christopher.how...@frigidcode.com wrote: On 08/12/2012 09:37 PM, Shakthi Kannan wrote: Hi, --- On Mon, Aug 13, 2012 at 10:51 AM, Christopher Howard christopher.how...@frigidcode.com wrote: | Say, for example, I have the list | [[1,2],[3,4]] and want to add 1 to each inner element, resulting in | [[2,3],[4,5]]. \-- Like this? ghci let xxs = [[1,2], [3,4]] ghci [ [ x+1 | x - xs] | xs - xxs ] [[2,3],[4,5]]
Beginners Digest, Vol 50, Issue 17
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cabal install errors (Benjamin Edwards) 2. Re: cabal install errors (damodar kulkarni) 3. source code for Generics for the Masses (Michael Litchard) 4. Error compiling OpenGL tutorial part 2 (Darren Grant) -- Message: 1 Date: Wed, 15 Aug 2012 12:04:15 +0100 From: Benjamin Edwards edwards.b...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors To: damodar kulkarni kdamodar2...@gmail.com Cc: haskellbeginners beginners@haskell.org Message-ID: can6k4nhm7rv3r9rudpprl7fpfpe_nawuwos3sjk26ndfmua...@mail.gmail.com Content-Type: text/plain; charset=windows-1252 Ironically enough, cabal is an acronym: Common Architecture for Building Applications and Libraries. Look ma, no packages! It is shame that almost every new-comer gets burnt by this in one way or another. I might have a crack at suggesting some re-writes, or extra caveats to the cabal docs. On Aug 15, 2012 5:39 AM, damodar kulkarni kdamodar2...@gmail.com wrote: Please see this: http://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-is-not-a-package-manager/ it is unfortunately true that cabal documentation is very misleading to many, especially the beginners ... that's why so many of us need to repeat after-an-expert that cabal-is-not-a-package-manager ... But now take a look at how many times the cabal user guide mentions the term package in its documentation, it is very easy to get misled... Cabal specifies a standard way in which Haskell libraries and applications can be *packaged* so that it is easy for consumers to use them, or * re-package* them, regardless of the Haskell implementation or installation platform. Cabal defines a common interface ? the *Cabal package* ? between *package authors, builders and users*. There is a library to help package authors implement this interface, and a tool to enable developers, builders and users *to work with Cabal packages*. taken from http://www.haskell.org/cabal/users-guide/ cabal should have been called haskell-make or hmake or something alike... thanks Benjamin, for the cabal-dev, hsenv tip though. -Damodar On Tue, Aug 14, 2012 at 5:38 PM, Benjamin Edwards edwards.b...@gmail.comwrote: I think one point bears repeating: cabal is a build system, really. It does a good enough job of that. It is a *terrible* package manager and using it as one I think is a classic mistake that the community needs to address. My two-penneth worth is this: Use cabal-dev, or hsenv, for *everything* and 99% of your woes will go away. The the only thing I do when getting haskell up and running is to get cabal-dev installed and it's dependencies in the cabal per user pkg store and then cabal-dev sandboxes for everything from then on. On Aug 14, 2012 11:57 AM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: On 08/13/12 22:19, Gregory Guthrie wrote: Thanks, I'll try that, but it looks like it could be a lot of maintenance and manual cleanup! I haven't knowingly done any manual upgrades of core packages, but I have done updates as asked by cabal when it thinks the database is getting old. I have had such pedestrian usage that I would not have expected to have goofed up the database! :-) Cabal seems to be more troublesome that other various *package managers* like apt, etc... Please see this: http://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-is-not-a-package-manager/ But yes, cabal or not, I agree that there should be a better system for managing haskell packages, like pip, gem or cpan... but that boils down to the problem that some has to do it, and people who are able to do it** are often too busy for that. ** and that doesn't include me, as I'm just starting to explore Haskell on my spare time. All in all, cabal suits me even with its idiosyncrasies. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120815/09e28ac3/attachment-0001.htm -- Message: 2 Date: Wed, 15 Aug 2012 21:36:42 +0530
Beginners Digest, Vol 50, Issue 19
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. convert to fixed length Int (Christopher Howard) 2. Re: convert to fixed length Int (Carlos J. G. Duarte) 3. Re: cabal install errors issues (Antoine Latter) 4. Re: cabal install errors issues (Gregory Guthrie) 5. Re: cabal install errors issues (Antoine Latter) 6. Re: cabal install errors issues (Brandon Allbery) 7. Re: cabal install errors issues (Gregory Guthrie) 8. Re: cabal install errors issues (Antoine Latter) 9. Re: cabal install errors issues (Gregory Guthrie) -- Message: 1 Date: Thu, 16 Aug 2012 16:42:08 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] convert to fixed length Int To: Haskell Beginners beginners@haskell.org Message-ID: 502d9360.8070...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 Hi. In Haskell, how would I go about converting from a Double (or Float) type to a Data.Int.Int8, Data.Int.Int16, and so forth? (Of course, expecting rounding and damage to out of range values.) I was playing around with signal generation using trig functions (hence the floating types) but the actual output has to be Int16. -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 554 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120816/10ff76fd/attachment-0001.pgp -- Message: 2 Date: Fri, 17 Aug 2012 02:06:14 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: Re: [Haskell-beginners] convert to fixed length Int To: beginners@haskell.org Message-ID: 502d9906.30...@gmail.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 08/17/12 01:42, Christopher Howard wrote: Hi. In Haskell, how would I go about converting from a Double (or Float) type to a Data.Int.Int8, Data.Int.Int16, and so forth? (Of course, expecting rounding and damage to out of range values.) I was playing around with signal generation using trig functions (hence the floating types) but the actual output has to be Int16. Don't know if there's a better or correct way, but this seems to work: ghci let c = (round 256.6) :: Int16 ghci :type c c :: Int16 It rolls over at overflow: ghci let c = (round 65537) :: Int16 ghci c 1 -- Message: 3 Date: Thu, 16 Aug 2012 21:21:56 -0500 From: Antoine Latter aslat...@gmail.com Subject: Re: [Haskell-beginners] cabal install errors issues To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org beginners@haskell.org Message-ID: cakjsnqhe-wmtndmyjo0b1rqtwxvetbs3qxiieqfonmkay_b...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Thu, Aug 16, 2012 at 8:18 AM, Gregory Guthrie guth...@mum.edu wrote: Thanks for the advice and pointers, I will try to make this transition, but it looks like it is not so simple. Trying to bootstrap into cabal-dev seems to require some external installations as well; cabal install cabal-dev --force-reinstalls Maybe I'm missing some context, but is there a reason you're using the --fore-reinstalls flag? If you didn't pass that then 'cabal' maybe would not try to re-install the 'network' package and you wouldn't run into this. Antoine -- Message: 4 Date: Thu, 16 Aug 2012 21:30:25 -0500 From: Gregory Guthrie guth...@mum.edu Subject: Re: [Haskell-beginners] cabal install errors issues To: Antoine Latter aslat...@gmail.com Cc: beginners@haskell.org beginners@haskell.org Message-ID: 08ef9da445c4b5439c4733e1f35705ba01e267667...@mail.cs.mum.edu Content-Type: text/plain; charset=utf-8 Yes, because a simple cabal install failed, and said the only way to do it was to force-installs. But if this is a dependency, wouldn't it be requires (or not) either way? --- -Original Message- Trying to bootstrap into cabal-dev seems to require some external installations as well; cabal install cabal-dev --force-reinstalls Maybe I'm missing some context, but is there a reason you're using the --fore-reinstalls flag? If you didn't pass that then 'cabal' maybe would not try to re-install the 'network' package and you wouldn't run into this. -- Message: 5 Date: Thu, 16 Aug 2012 21:36:54 -0500 From:
Beginners Digest, Vol 50, Issue 20
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: cabal install errors issues (Andres L?h) 2. 99problems: different response from ghci --runhaskell / ghc (GiGi) 3. Re: 99problems: different response from ghci -- runhaskell / ghc (Andres L?h) -- Message: 1 Date: Fri, 17 Aug 2012 10:16:34 +0200 From: Andres L?h andres.l...@googlemail.com Subject: Re: [Haskell-beginners] cabal install errors issues To: Antoine Latter aslat...@gmail.com Cc: Gregory Guthrie guth...@mum.edu, beginners@haskell.org beginners@haskell.org Message-ID: caljd_v5edgzm-3xf43p7rwdko5u_aj8cpmgnuxc_kby7v4d...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi. Sorry for singling out this one message of the thread to reply to a bunch of messages. Can you try upgrading cabal-install to see if the new solver handles it better? I think the new version works with what is in the platform. If you also get errors there might be ways to make it go ... I just tried installing cabal-dev on a clean platform, and I can confirm it doesn't work: $ cabal install --dry-run cabal-dev Resolving dependencies... In order, the following would be installed: tar-0.3.2.0 (new package) transformers-0.2.2.0 (new version) mtl-2.0.1.0 (new version) parsec-3.1.3 (new version) network-2.3.1.0 (new version) HTTP-4000.2.3 (reinstall) changes: mtl-2.1.1 - 2.0.1.0, network-2.3.0.13 - 2.3.1.0, parsec-3.1.2 - 3.1.3 cabal-dev-0.9.1 (new package) Warning: The following packages are likely to be broken by the reinstalls: haskell-platform-2012.2.0.0 Use --force-reinstalls if you want to install anyway. Investigating the dependencies, it seems cabal-dev depends on transformers 0.3, which in turn leads to an older mtl being picked, and all the other problems. I've only just come to this thread. There are a couple of things that are strange. The original poster shows logs where base version changes are listed. That's really puzzling to me. GHC usually has one version of base installed, and that can't be changed. So why are there several? Also, there are multiple versions of the Haskell Platform being listed as possibly being broken. How can multiple versions of the platform be installed at once? So something to me looks to be strange with that installation. There also seems to be a misconception that switching to cabal-dev means no longer using cabal-install. I just want to clarify that this isn't the case. The use of cabal-dev offers additional sandboxing functionality and wraps cabal-install, but you're still using it. The next release of cabal-install (don't know when that'll happen though, unfortunately) will most likely have sandboxing functionality built-in. Cheers, Andres -- Message: 2 Date: Fri, 17 Aug 2012 10:53:19 +0200 From: GiGi looee...@gmail.com Subject: [Haskell-beginners] 99problems: different response from ghci --runhaskell / ghc To: beginners@haskell.org Message-ID: CAEp_LLwrn8njTCjOnATp8vGOOOMcw-f=wno_971alqfjwjx...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hi all, trying to solve the problem 6 reverse a list I'm getting a different behaviour from ghci / runhaskell. main = do putStrLn $ concat (map show (myReverse [1,2,3])) -- putStrLn $ concat (map show (myReverse [])) myReverse :: [a] - [a] myReverse [] = [] myReverse (x:xs) = go [] (x:xs) where go :: [a] - [a] - [a] go curr (x:xs) | null xs = [x] ++ curr go curr (x:xs) = go ([x] ++ curr) xs the second putStrLn (once uncommented) gives this error in the runhaskell/ghc: Ambiguous type variable `a0' in the constraint: (Show a0) arising from a use of `show' Probable fix: add a type signature that fixes these type variable(s) In the first argument of `map', namely `show' _but_ if I load the same source into ghci I can successfully enterrun the command: Prelude :reload [1 of 1] Compiling Main ( 05.hs, interpreted ) Ok, modules loaded: Main. *Main putStrLn $ concat (map show (myReverse [])) *Main Then if I help the type inference changing the myReverse type declaration to: myReverse :: [Int] - [Int] everything works well So, my question is: _where_ is the difference between ghci / runhaskell? thx -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120817/9a35fbe3/attachment-0001.htm
Beginners Digest, Vol 50, Issue 21
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: 99problems: different response from ghci -- runhaskell / ghc (GiGi) 2. Re: Backtrace when a certain location in the code is executed (alex-hask...@copton.net) 3. Re: Error compiling OpenGL tutorial part 2 (Andrey Yankin) 4. Re: Backtrace when a certain location in the code is executed (Nathan H?sken) 5. Re: Backtrace when a certain location in the code is executed (Brandon Allbery) 6. Re: Error compiling OpenGL tutorial part 2 (Darren Grant) -- Message: 1 Date: Fri, 17 Aug 2012 14:31:59 +0200 From: GiGi looee...@gmail.com Subject: Re: [Haskell-beginners] 99problems: different response from ghci -- runhaskell / ghc To: Andres L?h and...@well-typed.com Cc: beginners@haskell.org Message-ID: caep_llx+6bposhsgendewi2aksnha3jkxsxz6gfwodx7yyp...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 thanks Andres On Fri, Aug 17, 2012 at 11:35 AM, Andres L?h and...@well-typed.com wrote: Hi. So, my question is: _where_ is the difference between ghci / runhaskell? See here: http://www.haskell.org/ghc/docs/latest/html/users_guide/interactive-evaluation.html#extended-default-rules Cheers, Andres -- Andres L?h, Haskell Consultant Well-Typed LLP, http://www.well-typed.com -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120817/5f32369d/attachment-0001.htm -- Message: 2 Date: Fri, 17 Aug 2012 14:45:06 +0200 From: alex-hask...@copton.net Subject: Re: [Haskell-beginners] Backtrace when a certain location in the code is executed To: beginners@haskell.org Message-ID: 20120817124506.GA3329@apus Content-Type: text/plain; charset=iso-8859-1 Hi On Thu, Aug 16, 2012 at 04:31:47PM +0200, Nathan H?sken wrote: I am trying to understand haskell program not written by me. During runtime one function is called with parameters which makes the function throw an error. I want to know from where the function is called. The execution model of Haskell is completely different. Actually, code locations are not executed. Instead, expressions are evaluated. And to make things worse, this evaluation is performed lazyly. So there is no stack trace as you know it from C++. There is one nice hack, though, that often helps in such situations. The module Debug.Trace exports a handy function 'trace :: String - a - a'. It always returns the second argument but outputs the String to stdout as a side effect. The hack is, that this function can be called in pure code! (No IO type involved). So, go to all locations in your code where you call the function is question and wrap the calls into a trace each. Greetings Alex -- next part -- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 198 bytes Desc: Digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120817/96c7238a/attachment-0001.pgp -- Message: 3 Date: Fri, 17 Aug 2012 18:06:22 +0400 From: Andrey Yankin yankin...@gmail.com Subject: Re: [Haskell-beginners] Error compiling OpenGL tutorial part 2 To: Darren Grant therealklu...@gmail.com Cc: beginners@haskell.org Message-ID: canxq4z2ommm-0tvosgw0n6an2q4h6vti1pq5wtlzmjqdkwr...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi! Try to group points and 7 with parentheses or put $ before points, since points became a function at this step in tutorial. But error message is a real mystery. How could the actual type of mapM_ be unit? Can somebody here explain this, please? Is unit a monad? 2012/8/16 Darren Grant therealklu...@gmail.com: I am currently following the OpenGL tutorial here: http://www.haskell.org/haskellwiki/OpenGLTutorial2 But in the current incarnation of Display.hs (http://pastebin.com/g4NekDVh) I am getting the following error: $ cabal install Resolving dependencies... Configuring mygl-0.1... Preprocessing executables for mygl-0.1... Building mygl-0.1... [3 of 5] Compiling Display ( Display.hs, dist\build\mygl\mygl-tmp\Display.o ) Display.hs:13:9: Couldn't match expected type `IO a0' with actual type `()' In the return type of a call of `mapM_' In a stmt of a 'do' expression: mapM_ (\ (x, y, z) - preservingMatrix
Beginners Digest, Vol 50, Issue 23
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Good style on . and $ pipeline? (Carlos J. G. Duarte) 2. Re: Good style on . and $ pipeline? (Darren Grant) 3. Re: Good style on . and $ pipeline? (Brent Yorgey) 4. Re: Good style on . and $ pipeline? (koomi) 5. Re: Good style on . and $ pipeline? (Felipe Almeida Lessa) 6. The Holy Trinity of Functional Programming (Costello, Roger L.) 7. Re: Good style on . and $ pipeline? (Ozgur Akgun) -- Message: 1 Date: Tue, 21 Aug 2012 21:34:49 +0100 From: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Subject: [Haskell-beginners] Good style on . and $ pipeline? To: beginners@haskell.org Message-ID: 5033f0e9.1040...@gmail.com Content-Type: text/plain; charset=us-ascii An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120821/a699e877/attachment-0001.htm -- Message: 2 Date: Tue, 21 Aug 2012 13:43:37 -0700 From: Darren Grant therealklu...@gmail.com Subject: Re: [Haskell-beginners] Good style on . and $ pipeline? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: ca+jd6sihau_pkxw5zyh1xtj848ejkwrsw8wabjoxnuhzcwo...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I am very new to Haskell, but what I've discovered so far is that the application operator $ is used to improve code readability. It can sometimes be used eliminate the need for parentheses that break natural left-to-right reading. Hoogle covers an example: http://hackage.haskell.org/packages/archive/base/latest/doc/html/Prelude.html#v:-36- Cheers! On Tue, Aug 21, 2012 at 1:34 PM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: Hi. Often I see the following pattern to build function pipelines: x = f1 . f2 $ fn arg They use the $ just before the last function call. I never got much into it: when to use the . or the $? I think today I figured it out: = . is a function composition operator: used to merge functions; = $ is a function application operator: used to apply a function to its arguments. If this reasoning is correct, I think the following should be a more adequate pattern: x = f1 . f2 . fn $ arg To merge/compose all functions first and apply the composed function to its parameter(s). Am I correct on this? Thx ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Tue, 21 Aug 2012 16:43:53 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Good style on . and $ pipeline? To: beginners@haskell.org Message-ID: 20120821204353.ga22...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Tue, Aug 21, 2012 at 09:34:49PM +0100, Carlos J. G. Duarte wrote: Hi. Often I see the following pattern to build function pipelines: x = f1 . f2 $ fn arg They use the $ just before the last function call. I never got much into it: when to use the . or the $? I think today I figured it out: = . is a function composition operator: used to merge functions; = $ is a function application operator: used to apply a function to its arguments. If this reasoning is correct, I think the following should be a more adequate pattern: x = f1 . f2 . fn $ arg To merge/compose all functions first and apply the composed function to its parameter(s). Am I correct on this? Thx Yes, you are absolutely correct. But sometimes people do something like f1 . f2 $ fn arg if for some reason they are thinking of fn arg as a primitive starting point, and then applying a pipeline of functions f2, f1 to that. But it is really just a different point of view. In any case, both (f1 . f2 . fn $ arg) and (f1 . f2 $ fn arg) are perfectly good style. Having more than one $, like (f1 $ f2 $ fn $ arg), is frowned upon. -Brent -- Message: 4 Date: Wed, 22 Aug 2012 03:34:33 +0200 From: koomi ko...@hackerspace-bamberg.de Subject: Re: [Haskell-beginners] Good style on . and $ pipeline? To: beginners@haskell.org Message-ID: 50343729.1080...@hackerspace-bamberg.de Content-Type: text/plain; charset=ISO-8859-1 On 21.08.2012 22:43, Brent Yorgey wrote: Having more than one $, like (f1 $ f2 $ fn $ arg), is frowned upon. Care to explain why this is considered bad? I don't see anything
Beginners Digest, Vol 50, Issue 25
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Today's Topics:
1. Re: Good style on . and $ pipeline? (David Johnson)
2. Re: The Holy Trinity of Functional Programming (Jay Sulzberger)
3. Re: Good style on . and $ pipeline? (Keshav Kini)
--
Message: 1
Date: Wed, 22 Aug 2012 18:18:47 -0500
From: David Johnson djohnso...@gmail.com
Subject: Re: [Haskell-beginners] Good style on . and $ pipeline?
To: Brandon Allbery allber...@gmail.com
Cc: beginners@haskell.org
Message-ID:
CAAWB79hXYVg+2uGi3KDjo2ha=avtsn2c3owowktx4wzn+ry...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
agglutinative That is one crazy word.
On Wed, Aug 22, 2012 at 10:09 AM, Brandon Allbery allber...@gmail.comwrote:
On Tue, Aug 21, 2012 at 9:34 PM, koomi ko...@hackerspace-bamberg.dewrote:
On 21.08.2012 22:43, Brent Yorgey wrote:
Having more than one $, like (f1 $ f2 $ fn $ arg), is frowned upon.
Care to explain why this is considered bad? I don't see anything wrong
with this.
Experientially, we see it a lot in #xmonad from beginners combining stuff
together with a certain amont of cargo-culting (being beginners and usually
quite unfamiliar with Haskell).
I've been moving toward using ($) to separate logical phrases and (.)
within the phrases, to make it easier to see which things go with which.
Since layoutHook is rather agglutinative, this helps a lot.
--
brandon s allbery allber...@gmail.com
wandering unix systems administrator (available) (412) 475-9364 vm/sms
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Date: Wed, 22 Aug 2012 20:21:45 -0400 (EDT)
From: Jay Sulzberger j...@panix.com
Subject: Re: [Haskell-beginners] The Holy Trinity of Functional
Programming
To: beginners@haskell.org beginners@haskell.org
Message-ID: pine.neb.4.64.1208221520250.21...@panix3.panix.com
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
On Wed, 22 Aug 2012, Costello, Roger L. coste...@mitre.org wrote:
Hello Christopher,
But do you think you could provide a
more real world example of an application
of the Holy Trinity ideas?
A commonly cited real-world example that illustrates the first key idea
(recursive data type) is a binary tree:
data Tree = Node String Tree Tree | Leaf
The elements of this data type include:
Leaf
Node Root Leaf Leaf
Node Root (Node Left Leaf Leaf)
(Node Right Leaf Leaf)
And so forth.
Common functions on this data type include insertions, deletions, traversal.
I am not sure if there is a use for the infinite value of this data type.
/Roger
Let us leave aside two kind of things:
1. _|_
2. infinite things
Let us define a signature Sig to be a structure like so:
1. We have a finite set Names.
2. For each name a in Names we have a finite non-negative
integer, called the arity of a.
Note that we allow a name, say a, to have an arity of zero. Such
names are called constants in some formalisms and distinguished
from names with an arity greater than zero.
We define a structure, sometimes called a model or an algebra
with signature Sig, to be:
1. A nonempty set S.
2. For each name a of arity n we have a function f: S^n - S,
where
a. S^n is the Cartesian product of S
b. f is everywhere defined on S^n and f is single-valued
If we call our model M then we may use this notation:
1. The ground set of M is S, which we write as Ground(M).
2. The f associated to the name a is M(a).
We now define the set of terms, which set we call Terms, over our signature:
1. Given a name a and list of terms of length n, where n is the
arity of a, t0, t1, .. t(n-1) the list a, t0, t1, ... t(n-1) is a
term.
2. Terms is the minimal set which satisfies 1.
Now, given a signature Sig, we may translate this setup into Haskell.
We do an example. Let Sig be given as follows:
Names is the set {a, b, c, d, e, f}.
The arities are
a has arity 0
b has arity 0
c has arity 0
d has arity 1
e has arity 2
f has arity 5
the set Terms over Sig is in one to one correspondence with
Beginners Digest, Vol 50, Issue 26
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. cabal: updating a package (Obscaenvs) 2. Re: cabal: updating a package (Andres L?h) 3. How to deal with recursive/missing dependencies? (Ming Gao) -- Message: 1 Date: Thu, 23 Aug 2012 12:39:25 +0200 From: Obscaenvs obscae...@gmail.com Subject: [Haskell-beginners] cabal: updating a package To: beginners@haskell.org Message-ID: 5036085d.7050...@gmail.com Content-Type: text/plain; charset=iso-8859-1; Format=flowed Hi there! Excuse me, but I am a bit bewildered; should I really have to give cabal --force-reinstalls to upgrade yesod to the new version 1.1.0.2? It says a lot of packages are likely to be broken, as per the paste http://pastebin.com/cYdZkShu. I was under the impression I had RTFM, but maybe I have missed something? /Fredrik -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120823/b90e3635/attachment-0001.htm -- Message: 2 Date: Thu, 23 Aug 2012 13:17:32 +0200 From: Andres L?h andres.l...@googlemail.com Subject: Re: [Haskell-beginners] cabal: updating a package To: Obscaenvs obscae...@gmail.com Cc: beginners@haskell.org Message-ID: CALjd_v7uDLDQs=rnkkonbucqz4k9bacdtyjcsd3nmxlspfd...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi. Hi there! Excuse me, but I am a bit bewildered; should I really have to give cabal --force-reinstalls to upgrade yesod to the new version 1.1.0.2? It says a lot of packages are likely to be broken, as per the paste http://pastebin.com/cYdZkShu. I strongly suggest not to use --upgrade-dependencies. It's probably unavoidable to break *some* (Yesod-related) packages for a framework with as many dependencies as Yesod has, unless you use sandboxing. But you shouldn't go ahead installing something if packages like bin-package-db or ghc appear among the ones that are going to be broken. I've just tested that starting from the 2012.2.0.0 platform and yesod-platform-1.0.4.2, a simple $ cabal install --dry-run yesod yields Resolving dependencies... In order, the following would be installed: clientsession-0.8.0 (new version) conduit-0.5.2.3 (new version) attoparsec-conduit-0.5.0 (new version) blaze-builder-conduit-0.5.0 (new version) http-types-0.7.3 (new version) network-conduit-0.5.0 (new version) shakespeare-1.0.1.1 (new version) hamlet-1.1.0.2 (new version) shakespeare-css-1.0.1.4 (new version) shakespeare-i18n-1.0.0.2 (reinstall) changes: shakespeare-1.0.0.2 - 1.0.1.1 shakespeare-js-1.0.0.5 (new version) shakespeare-text-1.0.0.4 (new version) simple-sendfile-0.2.6 (new version) stringsearch-0.3.6.3 (new package) tar-0.4.0.0 (new package) unix-time-0.1.2 (new package) fast-logger-0.2.2 (new version) monad-logger-0.2.0 (new package) persistent-1.0.0 (new version) persistent-template-1.0.0 (new version) wai-1.3.0 (new version) wai-logger-0.2.0 (new version) warp-1.3.0.1 (new version) xml-types-0.3.3 (new version) xml-conduit-1.0.3 (new version) yaml-0.8.0.1 (new version) yesod-routes-1.1.0 (new version) zlib-conduit-0.5.0 (new version) http-conduit-1.6.0 (new version) authenticate-1.3.1 (new version) wai-extra-1.3.0 (new version) yesod-core-1.1.1 (new version) yesod-json-1.1.0 (new version) yesod-persistent-1.1.0 (new version) yesod-form-1.1.1 (new version) yesod-auth-1.1.1 (new version) yesod-1.1.0.2 (new version) Warning: The following packages are likely to be broken by the reinstalls: yesod-platform-1.0.4.2 yesod-core-1.0.1.2 yesod-static-1.0.0.3 yesod-persistent-1.0.0.1 yesod-form-1.0.0.4 yesod-auth-1.0.2.1 yesod-1.0.1.6 yesod-json-1.0.0.1 yesod-default-1.0.1.1 Use --force-reinstalls if you want to install anyway. for me, which looks reasonably safe to do with --force-reinstalls. Cheers, Andres -- Message: 3 Date: Thu, 23 Aug 2012 22:02:43 +0200 From: Ming Gao m...@gmx.de Subject: [Haskell-beginners] How to deal with recursive/missing dependencies? To: beginners@haskell.org Message-ID: 50368c63.6080...@gmx.de Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hello, I ran into some dependency issues with cabal/ghc and could not find any solution on the internet. ghc-pkg check returns nothing, I suppose this is a good thing. But ghc -v returns: - Glasgow Haskell Compiler, Version 7.4.1, stage 2 booted by GHC version 7.4.1 Using binary package database:
Beginners Digest, Vol 50, Issue 28
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Difference between Monad composition and transformation (Song Zhang) 2. Re: shared files / environment / portability (Henk-Jan van Tuyl) -- Message: 1 Date: Sat, 25 Aug 2012 09:15:20 +0100 From: Song Zhang vxan...@gmail.com Subject: [Haskell-beginners] Difference between Monad composition and transformation To: beginners@haskell.org Message-ID: CACGMEOnGugMmzifyFR57z-mT_CFYDB5dMi3xnHsHHsi8NHC=h...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 When I use a State Monad transformer to combine with a Writer Monad StateT s (Writer w) a. is it different from composition of State Monad and Writer Monad. It is State s (Writer w a) ? StateT is defined as (s - m (a, s)), so StateT s (Writer w) a can be regarded as (s - Writer w a) , which is (s - ((a,w),s) and on the other hand State s (Writer w a) is (s - ((a,w),s). I suppose the are similar and if so, what is the point we still get Monad transformers? Thanks -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120825/acd963f9/attachment-0001.htm -- Message: 2 Date: Sat, 25 Aug 2012 10:28:17 +0200 From: Henk-Jan van Tuyl hjgt...@chello.nl Subject: Re: [Haskell-beginners] shared files / environment / portability To: Haskell Beginners beginners@haskell.org, Christopher Howard christopher.how...@frigidcode.com Message-ID: op.wjk8hfydpz0...@zen5.arnhem.chello.nl Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes On Sat, 25 Aug 2012 10:08:01 +0200, Henk-Jan van Tuyl hjgt...@chello.nl wrote: On Sat, 25 Aug 2012 08:09:04 +0200, Christopher Howard christopher.how...@frigidcode.com wrote: I'm coding a resource tracker for a game that loads images, sounds, etc. from files, and wondering how the program will know where the files are located on the installation system. (With C/C++ programs I usually had the build system hardcode the appropriate share/ directory into the config.h file.) Assuming I package for cabal distribution, what approaches to this problem are available to me? You can find an example in wxAsteroids[0], look at the main function. Another example can be found in the FRP version of wxAsteroids[1], e.g.: rock= bitmap $ getDataFile rock.ico Regards, Henk-Jan van Tuyl [1] https://github.com/HeinrichApfelmus/reactive-banana/blob/master/reactive-banana-wx/src/Asteroids.hs -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming -- -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 50, Issue 28 *
Beginners Digest, Vol 50, Issue 29
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Difference between Monad composition and transformation (Dennis Raddle) 2. Re: Difference between Monad composition and transformation (Brent Yorgey) 3. Re: MonadError (Nick Vanderweit) 4. Re: associative arrays (Nick Vanderweit) -- Message: 1 Date: Sat, 25 Aug 2012 03:14:02 -0700 From: Dennis Raddle dennis.rad...@gmail.com Subject: Re: [Haskell-beginners] Difference between Monad composition and transformation To: Haskell Beginners beginners@haskell.org Message-ID: CAKxLvoobf=nxutmq005ykp5iti9egat4emtmv1v_bj+ydqr...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I'm not exactly a Haskell beginner but haven't grasped much of it yet. I have a feeling the answer to your question has something to do with the fact that the monad transformer library provides instances that allow the use of, for example, get and put in any transformed monad that has a StateT somewhere in it. Or throwError in anything that has an ErrorT in it. In other words, you don't need to lift everything into the right level. Okay, that's a crude way of putting it, but someone will probably come along and clarify. Dennis On Sat, Aug 25, 2012 at 1:15 AM, Song Zhang vxan...@gmail.com wrote: When I use a State Monad transformer to combine with a Writer Monad StateT s (Writer w) a. is it different from composition of State Monad and Writer Monad. It is State s (Writer w a) ? StateT is defined as (s - m (a, s)), so StateT s (Writer w) a can be regarded as (s - Writer w a) , which is (s - ((a,w),s) and on the other hand State s (Writer w a) is (s - ((a,w),s). I suppose the are similar and if so, what is the point we still get Monad transformers? Thanks ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120825/5d31f39b/attachment-0001.htm -- Message: 2 Date: Sat, 25 Aug 2012 08:34:10 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] Difference between Monad composition and transformation To: beginners@haskell.org Message-ID: 20120825123410.ga15...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Sat, Aug 25, 2012 at 03:14:02AM -0700, Dennis Raddle wrote: I'm not exactly a Haskell beginner but haven't grasped much of it yet. I have a feeling the answer to your question has something to do with the fact that the monad transformer library provides instances that allow the use of, for example, get and put in any transformed monad that has a StateT somewhere in it. Or throwError in anything that has an ErrorT in it. In other words, you don't need to lift everything into the right level. Well, not really, that's a separate thing to do with type classes like MonadState and MonadError. To answer the OP's question, literally composing monadic types does often give you a type similar to the transformer version. However, the point of composing monads is to give you a new, combined monad. If you just use the type (State s (Writer w a)) this is just a State computation which happens to return something of type Writer w a. Combining such things with = does not take the Writer into account at all. On the other hand, StateT s (Writer w) a is a separate type with a Monad instance that combines the effects of State and Writer. -Brent On Sat, Aug 25, 2012 at 1:15 AM, Song Zhang vxan...@gmail.com wrote: When I use a State Monad transformer to combine with a Writer Monad StateT s (Writer w) a. is it different from composition of State Monad and Writer Monad. It is State s (Writer w a) ? StateT is defined as (s - m (a, s)), so StateT s (Writer w) a can be regarded as (s - Writer w a) , which is (s - ((a,w),s) and on the other hand State s (Writer w a) is (s - ((a,w),s). I suppose the are similar and if so, what is the point we still get Monad transformers? Thanks ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners
Beginners Digest, Vol 50, Issue 30
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. How to switch off a RadioMenuiItem? (Pierre Michallet) -- Message: 1 Date: Sun, 26 Aug 2012 22:50:09 +0200 From: Pierre Michallet p.michal...@free.fr Subject: [Haskell-beginners] How to switch off a RadioMenuiItem? To: beginners haskell beginners@haskell.org Message-ID: 868D84E71F204D399FF858E28799CB10@medione9995867 Content-Type: text/plain; charset=iso-8859-1 Using Glade, I have created a menu which,among other things,has 2 radioMenuItems located in the same submenu. Both are in the off state when the program starts. In the following, I will refer to them as initiationCB and beginnerCB. The expected behavior is that these 2 options are exclusive ie clicking one when in the OFF state will turn it ON and turn the other OFF. In fact, the first time I click on initiationCB its associated checkbox is turned ON; a second click on it will not change its state. When beginnerCB is then clicked, it is turned ON but initiationCB is not turned OFF as expected, and from then on, the two items are ON and there is no way to turn them OFF. One surprising thing is that in the same menu there are 2 CheckMenuItems which, when clicked, change their state without any code written to obtain this behavior. I would have expected the same from RadioMenuItems. In an attempt to switch a RadioMenuItem OFF , I have added the following code: on initiationCB menuItemActivate do checkMenuItemSetActive initiationCB True When initiationCB is clicked (and turned ON as a consequence) the program blows up seeming in an infinite recursion. The Gtk2HS tutorial (chapter 7.2) gives an example of selective choices by defining actions in the file called by a UIManager to get the elements of the user interface and RadioActionEntry in the code. The problem is that I could not succeed in associating an action to a menu item in the Glade file (as done in the tutorial), and in case of success, I don't know whether a XmlGetWidget instruction would recognize it. So the question is : is there a way to implement a solution similar to the one described in the tutorial using Glade instead of the UIManager approach? Another odd thing to me is that the signal menuItemToggle is not raised when a radioMenuItem is clicked. Thanks in advance for your help p.michal...@free.fr -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120826/d03a26ba/attachment-0001.htm -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 50, Issue 30 *
Beginners Digest, Vol 50, Issue 31
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. IO / State / Do Syntax (Christopher Howard) 2. Re: IO / State / Do Syntax (Alexander Bernauer) 3. Errors involving rigid skolem types (Matthew Moppett) 4. Re: Errors involving rigid skolem types (Matthew Moppett) 5. Re: Errors involving rigid skolem types (Brent Yorgey) 6. Are tuples really needed? (Carlos J. G. Duarte) 7. Re: Are tuples really needed? (Kyle Murphy) -- Message: 1 Date: Mon, 27 Aug 2012 02:27:22 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] IO / State / Do Syntax To: Haskell Beginners beginners@haskell.org Message-ID: 503b4b8a.10...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 So, I'm still working with my resource tracker idea -- keeping images stored and organized inside a resource tracker structure that I can pass around to functions that need them. Let's say I want a function like so: code: initResources :: IO ResourceTracker The idea being that initResources loads the image files, stores them in the resource tracker (RT) structure, and returns the RT. I know I can do something like so: code: initResources = do pic1 - loadImage someimage.png -- IO function pic2 - loadImage someimage2.png -- ... and so on ... let rt = emptyResourceTracker in let rt' = storeImage rt pic1keyword pic1 in let rt'' = storeImage rt' pic2keyword pic2 in -- ... and so on, until finally: ... rt'' Obviously, all the let statements and apostrophes are undesirable. So, presumably what I need is to being using the State monad, yes? (I must confess I have only a vague understanding of the State monad, even after reading several tutorials.) But in my initResources function, how do I mix use of the IO and State do syntax, and still get what I want? I think this has something to do with Monad transformers, but I'm even less clear on how those work. -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 554 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120827/605a3eda/attachment-0001.pgp -- Message: 2 Date: Mon, 27 Aug 2012 13:49:35 +0200 From: Alexander Bernauer alex-hask...@copton.net Subject: Re: [Haskell-beginners] IO / State / Do Syntax To: Haskell Beginners beginners@haskell.org Message-ID: 20120827114935.GB4253@apus Content-Type: text/plain; charset=us-ascii Hi you don't need the State monad for your problem. Standard functional composition is enough: ---8--- initResources = let images = [someimage.png, someimage2.png] keywords = [pic1keyword, pic2keyword] in do pics - mapM loadImage images let rt = foldr go emptyResourceTracker $ zip pics keywords -- use rt where go (pic, kw) rt = storeImage rt kw pic ---8--- Anyways, if you are interested in Monad transformers in general, go check out http://book.realworldhaskell.org/read/monad-transformers.html HTH Alex -- next part -- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 198 bytes Desc: Digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120827/c5f15557/attachment-0001.pgp -- Message: 3 Date: Mon, 27 Aug 2012 23:21:55 +1000 From: Matthew Moppett matthewmopp...@gmail.com Subject: [Haskell-beginners] Errors involving rigid skolem types To: beginners@haskell.org Message-ID: CAMLEjZAAhWGQWnLP=qto-kk2xqjrry5r4pzekuwmpi7y7c3...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 The following code is intended as a first step towards creating a cyclical enumerable type, such that: (e.g.) [Cyc Friday .. Cyc Tuesday] would yield [Friday, Saturday, Sunday, Monday, Tuesday] module Cycle where newtype Cyc a = Cyc a deriving (Eq, Ord, Bounded, Show, Read) fromCyc :: Cyc a - a fromCyc (Cyc a) = a instance (Enum a, Bounded a) = Enum (Cyc a) where fromEnum = fromEnum . fromCyc toEnum n = Cyc x where (x, max) = (x', maxBound) :: (a, a) x' = toEnum $ n `mod` ((fromEnum max) - 1) This yields a kind of
Beginners Digest, Vol 50, Issue 32
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Are tuples really needed? (Peter Hall) -- Message: 1 Date: Tue, 28 Aug 2012 05:45:20 +0100 From: Peter Hall peter.h...@memorphic.com Subject: Re: [Haskell-beginners] Are tuples really needed? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: CAA6hAk4=YzoE+1D42jOh2iYmxpp6=ZN7OkB=d-dvuhs+q8r...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 They are just syntactic sugar. You can just as easily create your own tuple types: data Tuple2 a b = Tuple2 a b data Tuple3 a b c = Tuple3 a b c data Tuple4 a b c d = Tuple4 a b c d ..etc ...except it's pretty ugly and none of the built-in Prelude functions that use tuples will work with them (curry, uncurry, fst, snd, lookup, zip,..). Peter On 28 August 2012 02:47, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: Sorry if this question is too insane, but I was wondering if tuples are really needed in Haskell. I mean, could tuples be generally replaced by variables unroll (f x y z) and explicit data types, or are there some things only possible to do via tuples? Thx in advance (and sorry if this looks silly). ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 50, Issue 32 *
Beginners Digest, Vol 50, Issue 33
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: associative arrays (Adrien Haxaire) 2. Re: Are tuples really needed? (David McBride) 3. system call uses a different shell,or does not pick up the whole environment (Hong Yang) 4. Re: system call uses a different shell, or does not pick up the whole environment (Brent Yorgey) 5. Re: system call uses a different shell, or does not pick up the whole environment (Hong Yang) 6. Re: system call uses a different shell, or does not pick up the whole environment (Michael Orlitzky) -- Message: 1 Date: Tue, 28 Aug 2012 14:29:16 +0200 From: Adrien Haxaire adr...@haxaire.org Subject: Re: [Haskell-beginners] associative arrays To: beginners@haskell.org Message-ID: b1d249b8bef91dcc2b878b0e8e041...@haxaire.org Content-Type: text/plain; charset=UTF-8; format=flowed On Sat, 25 Aug 2012 09:11:30 -0600, Nick Vanderweit wrote: I'd still recommend Data.Map, since it's a much more efficient data structure for the task. They are implemented as a tree, which is fine as long as you do not want/need duplicates in your association list. They are also well documented and the extensive API will do most of what you'll need. I use them a lot. -- Adrien Haxaire www.adrienhaxaire.org | @adrienhaxaire -- Message: 2 Date: Tue, 28 Aug 2012 10:23:50 -0400 From: David McBride toa...@gmail.com Subject: Re: [Haskell-beginners] Are tuples really needed? To: Carlos J. G. Duarte carlos.j.g.dua...@gmail.com Cc: beginners@haskell.org Message-ID: CAN+Tr40Bf=UOv-cP00K-1UWxy=zh9Me=qwk-hzgcs1vlkmy...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Pattern matching makes tuples really useful. Sometimes you just want to return a pair of values and you don't feel like making a one off constructor for it. Eg: random :: (RandomGen g, Random a) = g - (a, g). Without tuples you'd have to have a one off type data RandomGenWithRandom g a = RGWR g a, which is overkill, when you just wanted two values. On Mon, Aug 27, 2012 at 9:47 PM, Carlos J. G. Duarte carlos.j.g.dua...@gmail.com wrote: Sorry if this question is too insane, but I was wondering if tuples are really needed in Haskell. I mean, could tuples be generally replaced by variables unroll (f x y z) and explicit data types, or are there some things only possible to do via tuples? Thx in advance (and sorry if this looks silly). __**_ Beginners mailing list Beginners@haskell.org http://www.haskell.org/**mailman/listinfo/beginnershttp://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120828/1ad23bed/attachment-0001.htm -- Message: 3 Date: Tue, 28 Aug 2012 09:58:16 -0500 From: Hong Yang hyang...@gmail.com Subject: [Haskell-beginners] system call uses a different shell, or does not pick up the whole environment To: beginners@haskell.org Message-ID: CA+_A4U5du4CTW=d+gq-hb4b7hz-vbmxlxsidukobobpbofl...@mail.gmail.com Content-Type: text/plain; charset=utf-8 Hi, I am trying to mimic mapM() at shell command line. I define the interface as mapm cmd2 cmd1, so cmd2 will be run for each of the cmd1 results. $_ can be used inside cmd2 to represent the current cmd1 result. For example, the command mapm'cp -pr $_ destination_dir/$_'ls copies everything under the current directory to the destination directory. The code is as follows: -- module Main where import System.Environment ( getArgs ) import System.Exit import System.IO import System.Process import Text.Regex import Text.Regex.Posix main = do hs_argv - getArgs if length hs_argv /= 2 then putStrLn wrong arguments! exitFailure else do let [cmd2, cmd1] = hs_argv (_, hOut, hErr, _) - runInteractiveCommand cmd1 err - hGetContents hErr hClose hErr if null err then do out - hGetContents hOut mapM (f cmd2) (lines out) else putStr err exitFailure f :: String - String - IO ExitCode f cmd2 item = system cmd2' where cmd2' = if cmd2 =~ \\$\\_::Bool then subRegex (mkRegex \\$\\_) cmd2 item else cmd2 -- It works, except one issue that is bothering me. If I issue
Beginners Digest, Vol 50, Issue 34
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Today's Topics:
1. Re: system call uses a different shell, or does not pick
up the whole environment (Matthew)
2. Re: system call uses a different shell, or does not pick
up the whole environment (Hong Yang)
3. Re: system call uses a different shell, or does not pick
up the whole environment (Brent Yorgey)
4. Re: system call uses a different shell, or does not pick
up the whole environment (Brandon Allbery)
--
Message: 1
Date: Tue, 28 Aug 2012 08:40:09 -0700
From: Matthew wonderzom...@gmail.com
Subject: Re: [Haskell-beginners] system call uses a different shell,
or does not pick up the whole environment
To: Hong Yang hyang...@gmail.com
Cc: beginners@haskell.org
Message-ID:
cab4w-sau24kx5yrufsokeh9yntg1pizpojakjhd23-4eao1...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
Not to further discourage you from experimenting, but xargs can also
run commands in parallel. Check out the -P argument. :)
On Tue, Aug 28, 2012 at 8:19 AM, Hong Yang hyang...@gmail.com wrote:
Hi Brent,
Thanks for the xargs command info. I did not know it before.
The other reason I want to play with my mapm version is eventually I want to
make it concurrent.
Thanks again,
Hong
On Tue, Aug 28, 2012 at 10:08 AM, Brent Yorgey byor...@seas.upenn.edu
wrote:
I do not know the solution to your problem -- dealing with shells,
environments, etc. can be tricky.
However, do you know about the 'xargs' command? E.g. your example
could be accomplished with
ls | xargs -L 1 -I{} cp -pr {} destination_dir/{}
-Brent
On Tue, Aug 28, 2012 at 09:58:16AM -0500, Hong Yang wrote:
Hi,
I am trying to mimic mapM() at shell command line. I define the
interface
as mapm cmd2 cmd1, so cmd2 will be run for each of the cmd1 results.
$_
can be used inside cmd2 to represent the current cmd1 result.
For example, the command
mapm'cp -pr $_ destination_dir/$_'ls
copies everything under the current directory to the destination
directory.
The code is as follows:
--
module Main where
import System.Environment ( getArgs )
import System.Exit
import System.IO
import System.Process
import Text.Regex
import Text.Regex.Posix
main = do
hs_argv - getArgs
if length hs_argv /= 2
then
putStrLn wrong arguments! exitFailure
else do
let [cmd2, cmd1] = hs_argv
(_, hOut, hErr, _) - runInteractiveCommand cmd1
err - hGetContents hErr
hClose hErr
if null err
then do
out - hGetContents hOut
mapM (f cmd2) (lines out)
else
putStr err exitFailure
f :: String - String - IO ExitCode
f cmd2 item = system cmd2'
where cmd2' = if cmd2 =~ \\$\\_::Bool
then subRegex (mkRegex \\$\\_) cmd2 item
else cmd2
--
It works, except one issue that is bothering me.
If I issue
mapm'lt $_'ls,
I get a bunch of
/bin/sh: lt: command not found,
while I expect it act the same as
mapm'ls -Alrt --color=auto $_'ls,
because lt is aliased to ls -Alrt --color=auto.
Notice /bin/sh above. My shell is actually tcsh. All the aliases are
in
~/.cshrc.
I tried replacing system cmd2' with
system (source ~/.cshrc; ++ cmd2')
and
system (tcsh -c ++ 'source ~/.cshrc; ++ cmd2' ++ '),
but they did not solve the problem.
Can someone please help me?
Thanks,
Hong
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Message: 2
Date: Tue, 28 Aug 2012 10:49:20 -0500
From: Hong Yang hyang...@gmail.com
Subject: Re: [Haskell-beginners] system call uses a different shell,
or does not pick up the whole environment
To: Matthew wonderzom...@gmail.com
Cc: beginners@haskell.org
Message-ID:
CA+_A4U7rDXfJ-715HzH3Lk=kvb4w8CW1ovu-F=sqvkmxkab...@mail.gmail.com
Content-Type: text/plain; charset=utf-8
Beginners Digest, Vol 50, Issue 36
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. IO vars (Corentin Dupont) 2. Re: IO vars (Mihai Maruseac) 3. Re: IO vars (Corentin Dupont) 4. Re: IO vars (Eugene Perederey) 5. Re: IO vars (Ozgur Akgun) -- Message: 1 Date: Wed, 29 Aug 2012 10:58:58 +0200 From: Corentin Dupont corentin.dup...@gmail.com Subject: [Haskell-beginners] IO vars To: beginners@haskell.org Message-ID: caeyhvmo7hw5gq3m5yzovadjex7q1pny05d12gtw8mr66a2b...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hi all, there is something very basic that it seems escaped me. For example with the following program f and g have type IO () and I can thread a value between the two using a file. Can I do the exact same (not changing the types of f and g) without a file?* f,g :: IO () **f = withFile toto WriteMode (flip hPutStr toto) g = withFile toto ReadMode hGetLine = putStrLn main = f g* Thanks and cheers, Corentin -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120829/43c5919f/attachment-0001.htm -- Message: 2 Date: Wed, 29 Aug 2012 11:04:06 +0200 From: Mihai Maruseac mihai.marus...@gmail.com Subject: Re: [Haskell-beginners] IO vars To: Corentin Dupont corentin.dup...@gmail.com Cc: beginners@haskell.org Message-ID: CAOMsUMJ4cNbK4tG5Afxg41KKcGwdTXudKRrd+Tf=p0yspfk...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 On Wed, Aug 29, 2012 at 10:58 AM, Corentin Dupont corentin.dup...@gmail.com wrote: Hi all, there is something very basic that it seems escaped me. For example with the following program f and g have type IO () and I can thread a value between the two using a file. Can I do the exact same (not changing the types of f and g) without a file? f,g :: IO () f = withFile toto WriteMode (flip hPutStr toto) g = withFile toto ReadMode hGetLine = putStrLn main = f g Of course: f,g :: IO () f = putStr Answer: g = print 42 Main f g Answer: 42 The () is threaded by , not the file content -- MM -- Message: 3 Date: Wed, 29 Aug 2012 11:21:06 +0200 From: Corentin Dupont corentin.dup...@gmail.com Subject: Re: [Haskell-beginners] IO vars To: Mihai Maruseac mihai.marus...@gmail.com Cc: beginners@haskell.org Message-ID: CAEyhvmqxMMqKJDh8aqmLUc6+wXj2GgeWTbfw=in833bh9qu...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hi Mihai, maybe the term thread in my mail is not correct. What I mean is that a value gets stored by f and discovered by g. *f,g :: IO () f = withFile toto WriteMode (flip hPutStr 42) g = withFile toto ReadMode hGetLine = (\s - putStrLn $ Answer: ++ s) main = f g* Is it possible to do the same without files (the types must remain IO())? On Wed, Aug 29, 2012 at 11:04 AM, Mihai Maruseac mihai.marus...@gmail.comwrote: On Wed, Aug 29, 2012 at 10:58 AM, Corentin Dupont corentin.dup...@gmail.com wrote: Hi all, there is something very basic that it seems escaped me. For example with the following program f and g have type IO () and I can thread a value between the two using a file. Can I do the exact same (not changing the types of f and g) without a file? f,g :: IO () f = withFile toto WriteMode (flip hPutStr toto) g = withFile toto ReadMode hGetLine = putStrLn main = f g Of course: f,g :: IO () f = putStr Answer: g = print 42 Main f g Answer: 42 The () is threaded by , not the file content -- MM -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120829/e386960c/attachment-0001.htm -- Message: 4 Date: Wed, 29 Aug 2012 02:28:45 -0700 From: Eugene Perederey eugene.perede...@gmail.com Subject: Re: [Haskell-beginners] IO vars To: Corentin Dupont corentin.dup...@gmail.com Cc: beginners@haskell.org Message-ID: CAFTqo156WjDWQ1BjrtCJdJQJwsb3PNw=ivzxc3-=m0zan35...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Of course, not. What you do with a file is a sequence of side effects done by f, then g. If you want to reuse the value of type IO a returned by f, your g function would need to have type g:: a-IO () so that you combine the actions: f = g On 29 August 2012 02:21, Corentin Dupont corentin.dup...@gmail.com wrote: Hi Mihai, maybe the term thread in my mail is not correct. What I mean is that a value
Beginners Digest, Vol 50, Issue 37
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than Re: Contents of Beginners digest...
Today's Topics:
1. Re: IO vars (Corentin Dupont)
2. Re: IO vars ACID (Corentin Dupont)
3. Re: complex typeclass/constraint question (Brent Yorgey)
4. Re: IO vars (Brent Yorgey)
5. How to load multiple source files in GHCi? (Yang)
6. Re: How to load multiple source files in GHCi?
(Alexander Bernauer)
7. Re: complex typeclass/constraint question (Dennis Raddle)
--
Message: 1
Date: Wed, 29 Aug 2012 12:00:50 +0200
From: Corentin Dupont corentin.dup...@gmail.com
Subject: Re: [Haskell-beginners] IO vars
To: Ozgur Akgun ozgurak...@gmail.com
Cc: beginners@haskell.org
Message-ID:
caeyhvmobyrqdkf4gseycf3axtat2u_hqlhnke2dtmzur9e4...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
Thanks Eugene and Ozgur.
I also looked on the side of IORef, but it doesn't looked to be a good
solution since we have to use unsafePerformIO.
I have a big program to modify, and I want to pass some new data to
existing functions of type IO(). I'd like to avoid changing all the
function's types down the chain... What is the best way to do that?
On Wed, Aug 29, 2012 at 11:43 AM, Ozgur Akgun ozgurak...@gmail.com wrote:
On 29 August 2012 10:21, Corentin Dupont corentin.dup...@gmail.comwrote:
*f,g :: IO ()
f = withFile toto WriteMode (flip hPutStr 42)
g = withFile toto ReadMode hGetLine = (\s - putStrLn $ Answer: ++
s)
main = f g*
Is it possible to do the same without files (the types must remain IO())?
One can use an IORef to get a similar effect.
import Data.IORef
import System.IO.Unsafe
{-# NOINLINE toto #-}
toto :: IORef String
toto = unsafePerformIO (newIORef )
f,g :: IO ()
f = writeIORef toto 42
g = readIORef toto = (\s - putStrLn $ Answer: ++ s)
main = f g
HTH,
Ozgur
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Message: 2
Date: Wed, 29 Aug 2012 12:12:34 +0200
From: Corentin Dupont corentin.dup...@gmail.com
Subject: Re: [Haskell-beginners] IO vars ACID
To: Ozgur Akgun ozgurak...@gmail.com
Cc: beginners@haskell.org
Message-ID:
CAEyhvmr8wHFxc3HZKa7P=G0V6R5UBSz=qcnr9rztfjsngvf...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
To give you more context, I have a soft using ACID state to store and
retrieve values.
For example I have a function like that:
newPlayer :: PlayerName - IO ()
newPlayer name = update $ AddPlayer name
It seems that ACID uses a global state or a file to store the events... I'd
like to suppress the ACID state for the moment, how should I do?
Change all the* IO () *types to *StateT Game IO ()*?
Indead the ACID state is started with:
c - localStartSystemState (Proxy :: Proxy Game)
Best,
C
On Wed, Aug 29, 2012 at 12:00 PM, Corentin Dupont corentin.dup...@gmail.com
wrote:
Thanks Eugene and Ozgur.
I also looked on the side of IORef, but it doesn't looked to be a good
solution since we have to use unsafePerformIO.
I have a big program to modify, and I want to pass some new data to
existing functions of type IO(). I'd like to avoid changing all the
function's types down the chain... What is the best way to do that?
On Wed, Aug 29, 2012 at 11:43 AM, Ozgur Akgun ozgurak...@gmail.comwrote:
On 29 August 2012 10:21, Corentin Dupont corentin.dup...@gmail.comwrote:
*f,g :: IO ()
f = withFile toto WriteMode (flip hPutStr 42)
g = withFile toto ReadMode hGetLine = (\s - putStrLn $ Answer: ++
s)
main = f g*
Is it possible to do the same without files (the types must remain IO())?
One can use an IORef to get a similar effect.
import Data.IORef
import System.IO.Unsafe
{-# NOINLINE toto #-}
toto :: IORef String
toto = unsafePerformIO (newIORef )
f,g :: IO ()
f = writeIORef toto 42
g = readIORef toto = (\s - putStrLn $ Answer: ++ s)
main = f g
HTH,
Ozgur
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Message: 3
Date: Wed, 29 Aug 2012 06:50:47 -0400
From: Brent Yorgey byor...@seas.upenn.edu
Subject: Re: [Haskell-beginners] complex typeclass/constraint question
To: beginners@haskell.org
Message-ID: 20120829105047.ga12...@seas.upenn.edu
Content-Type: text/plain; charset=us-ascii
On Wed, Aug 29, 2012 at 12:28:37AM -0700,
Beginners Digest, Vol 50, Issue 39
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: First version of GHC (Jonas Almstr?m Dureg?rd) 2. - (Patrick Redmond) 3. Re: - (David McBride) 4. Re: - (Tony Morris) 5. Re: - (Karl Voelker) -- Message: 1 Date: Thu, 30 Aug 2012 17:52:21 +0200 From: Jonas Almstr?m Dureg?rd jonas.dureg...@chalmers.se Subject: Re: [Haskell-beginners] First version of GHC To: D?niel Arat? exitcons...@gmail.com Cc: beginners@haskell.org Message-ID: cagngccbv0qdrfm7ppoa3b7c7j1nkfy+x3tebkjphgn8codz...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 According to A history of Haskell: being lazy with class, the LML prototype was indeed used to bootstrap the first Haskell version of GHC. Regards, Jonas On 30 August 2012 17:27, Jonas Almstr?m Dureg?rd jonas.dureg...@chalmers.se wrote: Hi, According to the GHC wikipedia page, a prototype was written in Lazy ML. Whether this prototype was used to bootstrap the Haskell version is not specified. Regards, Jonas On 30 August 2012 16:13, D?niel Arat? exitcons...@gmail.com wrote: Hi all, I'm curious if the first implementation of GHC was in a different language before its current instance could be developed. If yes, what language was used? If not, what compiler was first used to compile GHC? Thank you, Daniel ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 2 Date: Thu, 30 Aug 2012 23:00:52 -0400 From: Patrick Redmond plredm...@gmail.com Subject: [Haskell-beginners] - To: Haskell Beginners beginners@haskell.org Message-ID: cahuea4ewrehhe8clypyhoyhmjztw7pz1mvpg1db44+mn93b...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 I'm reading Learn You a Haskell for Great Good!, chapter 9, Input and Output http://learnyouahaskell.com/input-and-output. IO actions are given liberal coverage throughout the chapter, however it is never mentioned whether the value-extractor syntax (-) has a type or not. main = do x - getLine putStrLn $ reverse x In this little program, getLine has type IO String and x has type String. This implies to me that (-) has type IO a - a. However, GHCI chokes on :t (-) and Hoogle says it's just a syntactic element http://www.haskell.org/haskellwiki/Keywords#.3C-. I guess I don't have a specific question, but I was kind of expecting it to be a function with a type because everything seems to be a function with a type in Haskell... Thanks for listening! -- Message: 3 Date: Thu, 30 Aug 2012 23:09:08 -0400 From: David McBride toa...@gmail.com Subject: Re: [Haskell-beginners] - To: Patrick Redmond plredm...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: can+tr40mewv0dtmrp7yq58wki8nchcx4werurjycrgkoop4...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 It is a syntatic sugar that is expanded to getLine = \x - putStrLn $ reverse x = is defined in the typeclass for Monad. In general, if something is using - notation, it's type is Monad m = m a, where m could be any of many monads, IO, Maybe, [] (lists), Parser or even some type of yours that you made an instance of Monad, which you can do if you would like to use that syntax. On Thu, Aug 30, 2012 at 11:00 PM, Patrick Redmond plredm...@gmail.comwrote: I'm reading Learn You a Haskell for Great Good!, chapter 9, Input and Output http://learnyouahaskell.com/input-and-output. IO actions are given liberal coverage throughout the chapter, however it is never mentioned whether the value-extractor syntax (-) has a type or not. main = do x - getLine putStrLn $ reverse x In this little program, getLine has type IO String and x has type String. This implies to me that (-) has type IO a - a. However, GHCI chokes on :t (-) and Hoogle says it's just a syntactic element http://www.haskell.org/haskellwiki/Keywords#.3C-. I guess I don't have a specific question, but I was kind of expecting it to be a function with a type because everything seems to be a function with a type in Haskell... Thanks for listening! ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL:
Beginners Digest, Vol 50, Issue 40
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. A simple function V2 (Ezequiel Hernan Di Giorgi) 2. Re: A simple function V2 (Gary Klindt) 3. Re: A simple function V2 (Gary Klindt) 4. Re: A simple function V2 (Ertugrul S?ylemez) 5. Re: A simple function V2 (Lyndon Maydwell) 6. Re: A simple function V2 (Brent Yorgey) 7. Re: A simple function V2 (Ertugrul S?ylemez) -- Message: 1 Date: Fri, 31 Aug 2012 09:01:30 -0300 From: Ezequiel Hernan Di Giorgi hernan.digio...@gmail.com Subject: [Haskell-beginners] A simple function V2 To: beginners@haskell.org Message-ID: cahrx9sxsnwd-jjh2zy5bdhfrkzr+ed-c4c1tddpi8zbjyju...@mail.gmail.com Content-Type: text/plain; charset=utf-8 First i want to thank all the persons who responded me yesterday to help me. Thanks! I am so happy with with your friendliness. So i have other beginners question: Now i want a improved version of my* intercalate*. Now i want to call a function with two [t][t] and obtain another one which have only even elements, even because: - [1,2,3,3,4][6] and the ouput [1,6] - [1,2,3,4][5,6,7] output [1,5,2,6,3,7] I tried it: *intercalate :: (Eq t) = [t] - [t] - [t]* *intercalate (x:xs) (y:ys)* * | xt == [] = []* * | yt == [] = []* * | otherwise = x : y : intercalate xs ys* * where xt=(x:xs)* *yt=(y:ys)* but i get nice error **Main intercalate [1][6]* *[1,6*** Exception: baby.hs:(2,1)-(5,51): Non-exhaustive patterns in function intercalate* * * **Main * (yes...the file's name is baby.hs) Thanks in advance! (: (: (: (: (: -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120831/5b1e2b3b/attachment-0001.htm -- Message: 2 Date: Fri, 31 Aug 2012 14:06:02 +0200 From: Gary Klindt gary.kli...@googlemail.com Subject: Re: [Haskell-beginners] A simple function V2 To: Ezequiel Hernan Di Giorgi hernan.digio...@gmail.com Cc: beginners@haskell.org Message-ID: 5040a8aa.1070...@googlemail.com Content-Type: text/plain; charset=UTF-8; format=flowed Hi, you don't proof for empty lists, only for empty tails: (x:[]) On 08/31/2012 02:01 PM, Ezequiel Hernan Di Giorgi wrote: First i want to thank all the persons who responded me yesterday to help me. Thanks! I am so happy with with your friendliness. So i have other beginners question: Now i want a improved version of my* intercalate*. Now i want to call a function with two [t][t] and obtain another one which have only even elements, even because: - [1,2,3,3,4][6] and the ouput [1,6] - [1,2,3,4][5,6,7] output [1,5,2,6,3,7] I tried it: *intercalate :: (Eq t) = [t] - [t] - [t]* *intercalate (x:xs) (y:ys)* * | xt == [] = []* * | yt == [] = []* * | otherwise = x : y : intercalate xs ys* * where xt=(x:xs)* *yt=(y:ys)* but i get nice error **Main intercalate [1][6]* *[1,6*** Exception: baby.hs:(2,1)-(5,51): Non-exhaustive patterns in function intercalate* * * **Main * (yes...the file's name is baby.hs) Thanks in advance! (: (: (: (: (: ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Fri, 31 Aug 2012 14:16:06 +0200 From: Gary Klindt gary.kli...@googlemail.com Subject: Re: [Haskell-beginners] A simple function V2 To: Ezequiel Hernan Di Giorgi hernan.digio...@gmail.com Cc: beginners@haskell.org Message-ID: 5040ab06.8080...@googlemail.com Content-Type: text/plain; charset=UTF-8; format=flowed my mistake, that's not right. But you should try to use use something like this: intercalate :: (Eq t) = [t] - [t] - [t] intercalate _ [] = [] intercalate [] _ = [] intercalate (x:xs) (y:ys) = x : y : intercalate xs ys with the last line, you imply that your lists have at least one element (through pattern matching). By the recursive call, you will enter this 'non-exhaustive' case. Also, instead of writing *intercalate (x:xs) (y:ys)* * | xt == [] = []* * | yt == [] = []* * | otherwise = x : y : intercalate xs ys* * where xt=(x:xs)* *yt=(y:ys)* for defining xt and yt, you could write: intercalate xt@(x:xs) yt@(y:ys) greets On 08/31/2012 02:06 PM, Gary Klindt wrote: Hi, you don't proof for empty lists, only for empty tails: (x:[]) On 08/31/2012 02:01 PM, Ezequiel Hernan Di Giorgi wrote: First i want to thank all
Beginners Digest, Vol 50, Issue 41
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Today's Topics:
1. Warp and Yesod benchmark puzzle (Lorenzo Bolla)
2. factorial question (KMandPJLynch)
3. Re: factorial question (Brandon Allbery)
4. Re: factorial question (Nick Vanderweit)
5. Re: Warp and Yesod benchmark puzzle (Bryce)
6. Re: A simple function V2 (Brent Yorgey)
7. joining lists sharing multiple type classes (Christopher Howard)
8. Re: A simple function V2 (Ertugrul S?ylemez)
--
Message: 1
Date: Fri, 31 Aug 2012 15:24:19 +0100
From: Lorenzo Bolla lbo...@gmail.com
Subject: [Haskell-beginners] Warp and Yesod benchmark puzzle
To: beginners@haskell.org
Message-ID:
CADjgTRwWdzvSQ1Zxmk6zkvrsGeRdAeL++CBkRm=un-3i_+m...@mail.gmail.com
Content-Type: text/plain; charset=UTF-8
Hi all,
This is a question specific to the Yesod framework, but simple enough
(I hope) to be considered a beginner question...
I am puzzled by the performance of these two very simple web-servers,
one written in Warp and another written in Yesod:
=== YESOD ===
{-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses,
TemplateHaskell #-}
import Yesod
data HelloWorld = HelloWorld
mkYesod HelloWorld [parseRoutes|
/ HomeR GET
|]
instance Yesod HelloWorld
getHomeR :: Handler RepHtml
getHomeR = defaultLayout [whamlet|$newline always
Hello World!
|]
main :: IO ()
-- main = warpDebug 3000 HelloWorld
main = warp 3000 HelloWorld
=== WARP ===
{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.HTTP.Types
import Network.Wai.Handler.Warp (run)
import Data.ByteString.Lazy.Char8 ()
app :: Application
app _ = return $ responseLBS
status200
[(Content-Type, text/html)]
Hello, Warp!
main :: IO ()
main = do
putStrLn http://localhost:8080/;
run 8080 app
===
I've tested both using httperf:
$ httperf --hog --client=0/1 --server=localhost --port=3000 --uri=/
--rate=1000 --send-buffer=4096 --recv-buffer=16384 --num-conns=100
--num-calls=100 --burst-length=20
and I got very different results:
YESOD: Request rate: 4048.0 req/s (0.2 ms/req)
WARP: Request rate: 33656.2 req/s (0.0 ms/req)
Now, I understand that Yesod is expected to be slower than the raw
Warp, but I wasn't expecting a 10x slowdown, especially for such a
trivial Yesod app (no db, no auth, etc.).
[
Compilation command was: ghc -Wall -O2 --make yesod.hs
$ yesod version
yesod-core version:1.1.0
]
What is going on?
Thanks,
L.
--
Message: 2
Date: Fri, 31 Aug 2012 12:23:24 -0400
From: KMandPJLynch kmandpjly...@verizon.net
Subject: [Haskell-beginners] factorial question
To: beginners@haskell.org
Message-ID: e6b7f256-fc25-4755-a3a7-384379421...@verizon.net
Content-Type: text/plain; charset=us-ascii
Good afternoon,
I'm going thru Graham Hutton's book Programming in Haskell [and am viewing
the associated online lectures by Erik Meijer and Graham].
I find both to be excellent.
My problem is with the following statements:
factorial' :: Int - Int
factorial' 0= 1
factorial' (n+1) = (n+1)*factorial' n
When I load this into GHC I get the following error:
pihch01.hs:128:13: Parse error in pattern: n + 1
I'd appreciate any advice.
Good day
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Message: 3
Date: Fri, 31 Aug 2012 12:30:34 -0400
From: Brandon Allbery allber...@gmail.com
Subject: Re: [Haskell-beginners] factorial question
To: KMandPJLynch kmandpjly...@verizon.net
Cc: beginners@haskell.org
Message-ID:
CAKFCL4ULTGxrWbScJVnDUN_G1SFNX5==nbuqzvbzd4n7s77...@mail.gmail.com
Content-Type: text/plain; charset=utf-8
On Fri, Aug 31, 2012 at 12:23 PM, KMandPJLynch kmandpjly...@verizon.netwrote:
*factorial' :: Int - Int*
*factorial' 0= 1*
*factorial' (n+1) = (n+1)*factorial' n*
n+k patterns were removed from Haskell 2010. You can re-enable them in GHC
with
{-# LANGUAGE NPlusKPatterns #-}
or
{-# LANGUAGE Haskell98 #-}
as the first line of the source file.
--
brandon s allbery allber...@gmail.com
wandering unix systems administrator (available) (412) 475-9364 vm/sms
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Beginners Digest, Vol 51, Issue 1
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: joining lists sharing multiple type classes (Nick Vanderweit) 2. Re: joining lists sharing multiple type classes (Christopher Howard) 3. Re: Warp and Yesod benchmark puzzle (Felipe Almeida Lessa) 4. Re: Warp and Yesod benchmark puzzle (Lorenzo Bolla) 5. Re: Warp and Yesod benchmark puzzle (Krzysztof Skrz?tnicki) -- Message: 1 Date: Fri, 31 Aug 2012 15:13:41 -0600 From: Nick Vanderweit nick.vanderw...@gmail.com Subject: Re: [Haskell-beginners] joining lists sharing multiple type classes To: beginners@haskell.org Message-ID: 1544399.PW3MRytGsC@euler Content-Type: text/plain; charset=us-ascii It's not that your syntax is off, but rather that what you're trying to do doesn't really make sense in the Haskell type system. Lists are by nature parameterized over a single type. It is possible via existential types to have a list over a polymorphic type like: exists a. (Locatable a, Animation a) = a but this is doubtfully what you want. It suffers from the fact that, for a given list entry, you don't actually know what its type is, and so you can't do anything really useful here. So basically: you can't have two kinds of data types in a list. What you probably want is a data type, like: data Object = Star ... | Asteroid ... That is, rather than having two types that you're trying to put in a list, have one type with two data constructors. Then you *can* store them together, and write functions that operate via pattern matching on the various constructors. Hope that helps. Nick On Friday, August 31, 2012 11:34:40 AM Christopher Howard wrote: Hi. I've got two data structures, Star and Asteroid (eventually I'll make more) that both belong to the following type classes: Locatable, and Animation. I wanted to do something like so in part of the code: code: let stars = ... in -- of type [Star] let asteroids = ... in -- of type [Asteroid] let visibleObjects = do visibleObject - (stars ++ asteroids) ... -- prep each object for graphics system -- using funcs from both type classes ... -- feed visibleObjects to graphics system However, this does not work because the two lists are not automatically downgraded when joined together by (++). The compiler complains about asteroids not being of type [Star]. What is the simplest way to do what I am trying to do? I tried this, but I think my syntax is off: code: let visibleObjects = do visibleObject - ((stars :: [(Locatable a, Animation a) = a) ++ (asteroids :: [(Locatable a, Animation a) = a) ) Compiler complains about Illegal polymorphic or qualified type. -- Message: 2 Date: Fri, 31 Aug 2012 13:43:53 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: Re: [Haskell-beginners] joining lists sharing multiple type classes To: Haskell Beginners beginners@haskell.org Message-ID: 50413019.1030...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 On 08/31/2012 12:16 PM, Sergey Mironov wrote: Yes, you can't concat [Star] and [Asteroid] because they are of different type. Lets assume that Animation is defined as follows class Animation a where feed :: GraphicSystem - a - IO () -- feeds a to graphic system and we have instance Animation Star where ... instance Animation Asteroid where ... than we can do game_cycle :: ([Star],[Asteroid]) - GraphicSystem - IO () game_cycle world@(stars, asteroids) gs = do mapM (feed gs) stars mapM (feed gs) asteroids return () This would probably work, though it evades my principle inquiry, i.e., how to purposely downgrade multiple types which belong to the same type classes into a single type. but not game_cycle :: ([Star],[Asteroid]) - GraphicSystem - IO () game_cycle world@(stars, asteroids) gs = do mapM (feed gs) (stars ++ asteroids) -- type mismatch return () If you absolutly sure, that you really need a single list of all objects, consider using single type for them! data WorldObject = Star ... | Asteroid ... Sergey This approach is not modular... some of my types will be quite complex and I would rather have them as their own separate data types in their own module, rather than one monstrous type. Looking into this some
Beginners Digest, Vol 51, Issue 4
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. (no subject) (Dennis Raddle) 2. Re: (no subject) (Tony Morris) -- Message: 1 Date: Sun, 2 Sep 2012 20:32:13 -0700 From: Dennis Raddle dennis.rad...@gmail.com Subject: [Haskell-beginners] (no subject) To: Haskell Beginners beginners@haskell.org Message-ID: CAKxLvop6q48RC-YWhXS5vgGNu=zz8yz1dtvy56kj_cf_lef...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I wanted to run the map function from Data.Map, let's call it M.map, but inside a monad transformer stack including the Error monad. M.map has this type: M.map :: (Ord k) = (a - b) - Map k a - Map k b However, I want to use a mapping function that has type (Monad m) = a - m b (i.e. errors could be thrown during the computation, a log could be written, etc) I wrote the following. Any comments on this way of doing things? mapMapM :: (Monad m, Ord k) = (a - m b) - Map k a - m (Map k b) mapMapM g mapIn = do let h (k,a) = do b - g a return (k,b) y - mapM h (M.toAscList mapIn) return $ M.fromAscList y -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120902/58b36638/attachment-0001.htm -- Message: 2 Date: Mon, 03 Sep 2012 13:34:42 +1000 From: Tony Morris tonymor...@gmail.com Subject: Re: [Haskell-beginners] (no subject) To: beginners@haskell.org Message-ID: 50442552.7080...@gmail.com Content-Type: text/plain; charset=iso-8859-1 On 03/09/12 13:32, Dennis Raddle wrote: I wanted to run the map function from Data.Map, let's call it M.map, but inside a monad transformer stack including the Error monad. M.map has this type: M.map :: (Ord k) = (a - b) - Map k a - Map k b However, I want to use a mapping function that has type (Monad m) = a - m b (i.e. errors could be thrown during the computation, a log could be written, etc) I wrote the following. Any comments on this way of doing things? mapMapM :: (Monad m, Ord k) = (a - m b) - Map k a - m (Map k b) mapMapM g mapIn = do let h (k,a) = do b - g a return (k,b) y - mapM h (M.toAscList mapIn) return $ M.fromAscList y ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners You probably want to look at Data.Traversable#traverse. -- Tony Morris http://tmorris.net/ -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120903/901b0b52/attachment-0001.htm -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 51, Issue 4
Beginners Digest, Vol 51, Issue 5
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. TagLib (linuxlinux2006) 2. Error Loading Stdm.lhs in Haskell platform 2012 (Iwan Awaludin) 3. Re: Error Loading Stdm.lhs in Haskell platform 2012 (Eugene Perederey) 4. Re: programming with Error monad (Dennis Raddle) -- Message: 1 Date: Mon, 3 Sep 2012 19:55:09 +0400 From: linuxlinux2006 linuxlinux2...@rambler.ru Subject: [Haskell-beginners] TagLib To: beginners@haskell.org Message-ID: 1346687709.409781.3525.36...@saddam4.rambler.ru Content-Type: text/plain; charset=utf-8; Format=flowed Hello Please tell me why this program does not work: http://hpaste.org/74171 Tags in audio file are recorded correctly, other programs see them. Thanks for the help -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120903/9e16867d/attachment-0001.htm -- Message: 2 Date: Tue, 4 Sep 2012 12:08:20 +0700 From: Iwan Awaludin awalu...@gmail.com Subject: [Haskell-beginners] Error Loading Stdm.lhs in Haskell platform 2012 To: beginners@haskell.org Message-ID: CAHd5so7N7nX=diyk9Sv3+553gvqmXhWqGfgcHmAh=5xr0nh...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Dear Sir/Madam I Installed *Haskell Platform 2012.2.0.0 for Windowshttp://lambda.haskell.org/platform/download/2012.2.0.0/HaskellPlatform-2012.2.0.0-setup.exe *and try to load Stdm.lhs which is downloaded from http://www.dcs.gla.ac.uk/~jtod/discrete-mathematics/Stdm.lhs I have this error: stdm.lhs:1160:14: Parse error in pattern: n + 1 Failed, modules loaded: none. Is there anything I should do to make it right? Thank you. -- Iwan Awaludin -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120904/03d69915/attachment-0001.htm -- Message: 3 Date: Mon, 3 Sep 2012 23:46:49 -0700 From: Eugene Perederey eugene.perede...@gmail.com Subject: Re: [Haskell-beginners] Error Loading Stdm.lhs in Haskell platform2012 To: Iwan Awaludin awalu...@gmail.com Cc: beginners@haskell.org Message-ID: caftqo17cq4-h_ygjdqzfcfgsuh4eykn40ytge3x5kvxes+v...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 What version of ghc are you using? In recent versions ghc doesn't support pattern matching of expressions like (n+1). You can rewrite that factorial function as factorial n = n * factorial (n-1) instead. best, Eugene On 3 September 2012 22:08, Iwan Awaludin awalu...@gmail.com wrote: Dear Sir/Madam I Installed Haskell Platform 2012.2.0.0 for Windows and try to load Stdm.lhs which is downloaded from http://www.dcs.gla.ac.uk/~jtod/discrete-mathematics/Stdm.lhs I have this error: stdm.lhs:1160:14: Parse error in pattern: n + 1 Failed, modules loaded: none. Is there anything I should do to make it right? Thank you. -- Iwan Awaludin ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 4 Date: Mon, 3 Sep 2012 23:56:55 -0700 From: Dennis Raddle dennis.rad...@gmail.com Subject: Re: [Haskell-beginners] programming with Error monad To: Haskell Beginners beginners@haskell.org Message-ID: cakxlvor+oxe9bzrte9lxhar7v6larrfsmrdeyekkac1v6a6...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 No one replied to this, but I think I figured out why, when I am using the Error monad, that every statement in a do construct runs at least part way, whether or not its data is needed. The final output is a Left or Right value -- and because a Left anywhere can short-circuit the compuation that follows, there is no way for the program to decide on a final Left/Right output without running each computation (or at least up to the point where it's not a Left). On Sat, Sep 1, 2012 at 12:59 PM, Dennis Raddle dennis.rad...@gmail.comwrote: I recently completed a large project and started another one. The first project was about processing music, in particular taking MusicXML and/or Sibelius files (Sibelius is a music notation program) and producing MIDI files according to the specifications I wanted. The second project is about algorithmic music composition. To handle errors in the first project, I used throw to throw exceptions. Now I am using the Error monad...
Beginners Digest, Vol 51, Issue 6
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. space leak processing multiple compressed files (Ian Knopke) 2. monads / do syntax (Christopher Howard) 3. Re: monads / do syntax (Ozgur Akgun) 4. Re: space leak processing multiple compressedfiles (Lorenzo Bolla) 5. Re: space leak processing multiple compressedfiles (Ian Knopke) 6. Re: space leak processing multiple compressedfiles (Benjamin Edwards) 7. Re: space leak processing multiple compressed files (Michael Orlitzky) -- Message: 1 Date: Tue, 4 Sep 2012 11:00:48 +0100 From: Ian Knopke ian.kno...@gmail.com Subject: [Haskell-beginners] space leak processing multiple compressed files To: beginners@haskell.org Message-ID: CAC+f4w=PL_8CbaqjGtPy_bEHOUnCRfLUCDzC6a=6+0tzdtk...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi everyone, I have a collection of bzipped files. Each file has a different number of items per line, with a separator between them. What I want to do is count the items in each file. I'm trying to read the files lazily but I seem to be running out of memory. I'm assuming I'm holding onto resources longer than I need to. Does anyone have any advice on how to improve this? Here's the basic program, slightly sanitized: main = do -- get a list of file names filelist - getFileList testsetdir -- process each compressed file files - mapM (\x - do thisfile - B.readFile x return (Z.decompress thisfile) ) filelist display $ processEntries files putStrLn finished -- processEntries -- processEntries is defined elsewhere, but basically does some string processing per line, -- counts the number of resulting elements and sums them per file processEntries :: [B.ByteString] - Int processEntries xs = foldl' (\x y - x + processEntries (B.lines y)) 0 xs -- display a field that returns a number display :: Int - IO () display = putStrLn . show -- Message: 2 Date: Tue, 04 Sep 2012 04:03:28 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] monads / do syntax To: Haskell Beginners beginners@haskell.org Message-ID: 5045ee10.3040...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 What does the following do expression translate into? (I.e., using = operator and lambda functions.) code: h = do a - (return 1 :: IO Integer) b - (return 2) return (a + b + 1) -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 554 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120904/b3bac86d/attachment-0001.pgp -- Message: 3 Date: Tue, 4 Sep 2012 13:10:18 +0100 From: Ozgur Akgun ozgurak...@gmail.com Subject: Re: [Haskell-beginners] monads / do syntax To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: calzazpdcx_cgg1xkoezprbppb9xf7vhh5-qsu9w0owdueki...@mail.gmail.com Content-Type: text/plain; charset=utf-8 Hi, On 4 September 2012 13:03, Christopher Howard christopher.how...@frigidcode.com wrote: h = do a - (return 1 :: IO Integer) b - (return 2) return (a + b + 1) h = (return 1 :: IO Integer) = \ a - (return 2) = \ b - return (a + b + 1) HTH, Ozgur -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120904/faefb460/attachment-0001.htm -- Message: 4 Date: Tue, 4 Sep 2012 13:55:38 +0100 From: Lorenzo Bolla lbo...@gmail.com Subject: Re: [Haskell-beginners] space leak processing multiple compressed files To: Ian Knopke ian.kno...@gmail.com Cc: beginners@haskell.org Message-ID: cadjgtry+rh+nkon4jwnmtdt_b5nmypw-kqpkuwfdxscerxn...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 On Tue, Sep 4, 2012 at 11:00 AM, Ian Knopke ian.kno...@gmail.com wrote: main = do -- get a list of file names filelist - getFileList testsetdir -- process each compressed file files - mapM (\x - do thisfile - B.readFile x return (Z.decompress thisfile)
Beginners Digest, Vol 51, Issue 7
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: monads / do syntax (Thiago Negri) 2. Re: Error Loading Stdm.lhs in Haskell platform 2012 (Stephen Tetley) 3. Thread Blocking (mukesh tiwari) 4. Re: Thread Blocking (Eugene Perederey) 5. Re: Thread Blocking (mukesh tiwari) 6. Re: Thread Blocking (Eugene Perederey) -- Message: 1 Date: Tue, 4 Sep 2012 13:38:42 -0300 From: Thiago Negri evoh...@gmail.com Subject: Re: [Haskell-beginners] monads / do syntax To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CABLneZvsjXsVTinNrhJG9hUkW_01d3-O=jeuqpjashs-ccp...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Go line by line, except the last one: a) When you see the pattern a - b, just swap it with b = \s -; b) When you see the pattern b, put a at the end of the line. In your case: | h = (return 1 :: IO Integer) = \a - |return 2 = \b - |return (a + b + 1) An example when you have a line without an assignment (-), this: | h = do a - (return 1 :: IO Integer) |b - (return 2) |putStrLn Hello, world! |return (a + b + 1) Turns into: | h = (return 1 :: IO Integer) = \a - |return 2 = \b - |putStrLn Hello, world! |return (a + b + 1) 2012/9/4 Christopher Howard christopher.how...@frigidcode.com: What does the following do expression translate into? (I.e., using = operator and lambda functions.) code: h = do a - (return 1 :: IO Integer) b - (return 2) return (a + b + 1) -- Message: 2 Date: Tue, 4 Sep 2012 17:40:45 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] Error Loading Stdm.lhs in Haskell platform2012 To: Iwan Awaludin awalu...@gmail.com Cc: beginners@haskell.org Message-ID: CAB2TPRDoOVD_M4Br-=vfgdggakw0p3xukh1qtyrtt4h2pmc...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 The code for the book is written in Haskell '98, but recent versions of GHC default to Haskell2010. A salient difference between H98 and H2012 is the removed of n + k patterns which generates the error you are seeing. I can't find the exact command to use in the GHC docs to enable H98, but you could try the following old flag which disables GHCs extensions: ghci -fno-glasgow-exts -- Message: 3 Date: Wed, 5 Sep 2012 00:24:30 +0530 From: mukesh tiwari mukeshtiwari.ii...@gmail.com Subject: [Haskell-beginners] Thread Blocking To: beginners@haskell.org Message-ID: CAFHZvE9pKn7_EM9t=x3sfay3oqvnmrmk_7xe9ro9jswbqpn...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hello All I was going trough Real World Haskell and it says If we try to put a value into an MVar that is already full, our thread is put to sleep until another thread takes the value out. I wrote a simple code to block main import Data.List import Control.Concurrent fun m = do putMVar m 10 return () main = do m - newEmptyMVar forkIO $ fun m putMVar m 10 return () What I am expecting that main should be blocked at least couple of times but its behaving more deterministically. [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp Concurrent.hs [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o ) Linking Concurrent ... [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ I am expecting to get thread blocked indefinitely on MVar at least half the time. Could some one please tell me why this deterministic behavior ? Regards Mukesh Tiwari -- next part -- An HTML attachment was scrubbed... URL:
Beginners Digest, Vol 51, Issue 8
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Thread Blocking (Eugene Perederey) 2. XML output (Torsten Otto) 3. Re: Error Loading Stdm.lhs in Haskell platform 2012 (Stephen Tetley) 4. Re: Error Loading Stdm.lhs in Haskell platform 2012 (Carlos J. G. Duarte) 5. Re: Thread Blocking (Dean Herington Elizabeth Lacey) 6. Re: XML output (Manfred Lotz) -- Message: 1 Date: Tue, 4 Sep 2012 12:30:06 -0700 From: Eugene Perederey eugene.perede...@gmail.com Subject: Re: [Haskell-beginners] Thread Blocking To: mukesh tiwari mukeshtiwari.ii...@gmail.com Cc: beginners@haskell.org Message-ID: CAFTqo159L-jcLhCBPREP_Gdq5uCuX7iP1A0OGPaPYftM=ms...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Well, not 50/50 but not deterministically -- I've caught fun1-main1-fun2 sequence, main1-fun1-main2 is much more often. Since you are using -threaded, the Haskell threads are running on top of the OS threads, so I guess it depends on the OS scheduler. On 4 September 2012 12:27, Eugene Perederey eugene.perede...@gmail.com wrote: I added a few prints to your code fun m = do putStrLn fun1 putMVar m 10 putStrLn fun2 main = do m - newEmptyMVar forkIO $ fun m putStrLn main1 putMVar m 10 putStrLn main2 It works 50/50 for me in Mac OS X 10.6.8. On 4 September 2012 12:16, mukesh tiwari mukeshtiwari.ii...@gmail.com wrote: Hi Eugene Thank you for reply. On Wed, Sep 5, 2012 at 12:32 AM, Eugene Perederey eugene.perede...@gmail.com wrote: Why do you think main should block more than once? I see only two possible scenarios: the fun thread puts to mvar first thus blocking main, So at least in this case I should get thread blocked indefinitely in an MVar operation or 10 is put into mvar in main, blocking the other thread indefinitely. or main will execute and fun thread will die. There are 50 - 50 chance for this ( assuming both are equally likely ). I did some modification in my code and Now I am consistently getting Concurrent: thread blocked indefinitely in an MVar operation import Data.List import Control.Concurrent fun m = do putMVar m 10 return () main = do m - newEmptyMVar forkIO $ fun m putStrLn I am inside main putMVar m 10 return () [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp Concurrent.hs [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o ) Linking Concurrent ... [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 I am inside main Concurrent: thread blocked indefinitely in an MVar operation [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 I am inside main Concurrent: thread blocked indefinitely in an MVar operation [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 I am inside main Concurrent: thread blocked indefinitely in an MVar operation [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 I am inside main Concurrent: thread blocked indefinitely in an MVar operation [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 I am inside main Concurrent: thread blocked indefinitely in an MVar operation My question is why the outcome in first case is deterministic. Every time the code executing ( at least half the time main thread should be blocked ) . Regards Mukesh Tiwari On 4 September 2012 11:54, mukesh tiwari mukeshtiwari.ii...@gmail.com wrote: Hello All I was going trough Real World Haskell and it says If we try to put a value into an MVar that is already full, our thread is put to sleep until another thread takes the value out. I wrote a simple code to block main import Data.List import Control.Concurrent fun m = do putMVar m 10 return () main = do m - newEmptyMVar forkIO $ fun m putMVar m 10 return () What I am expecting that main should be blocked at least couple of times but its behaving more deterministically. [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp Concurrent.hs [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o ) Linking Concurrent ... [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2 [mukesh.tiwari@
Beginners Digest, Vol 51, Issue 9
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. unfamiliar syntax in class definition (Christopher Howard) 2. Re: unfamiliar syntax in class definition (Rodrigo Ribeiro) 3. Haskell seems setup for iterative numerics; i.e. a standard example is Newton's method where lazy evaluation ... (KC) 4. Re: [Haskell-cafe] Haskell seems setup for iterative numerics; i.e. a standard example is Newton's method where lazy evaluation ... (KC) 5. Re: Error Loading Stdm.lhs in Haskell platform 2012 (Iwan Awaludin) -- Message: 1 Date: Wed, 05 Sep 2012 04:13:25 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] unfamiliar syntax in class definition To: Haskell Beginners beginners@haskell.org Message-ID: 504741e5.50...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 The MonadState class is defined as: quote: class Monad m = MonadState s m | m - s where ...etc... Please explain the part | m - s, that is, the use of the pipe symbol and the right arrow symbol which follow MonadState s m. -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 554 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120905/0d54c145/attachment-0001.pgp -- Message: 2 Date: Wed, 5 Sep 2012 09:11:22 -0300 From: Rodrigo Ribeiro rodrigogribe...@gmail.com Subject: Re: [Haskell-beginners] unfamiliar syntax in class definition To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: caoviy-pgpzely4tbgyhmytqoajqbpqnnzlwvm6bdvk225v6...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Hi, This is a functional dependency: http://www.haskell.org/haskellwiki/Functional_dependencies [ ]s Rodrigo On Wed, Sep 5, 2012 at 9:13 AM, Christopher Howard christopher.how...@frigidcode.com wrote: The MonadState class is defined as: quote: class Monad m = MonadState s m | m - s where ...etc... Please explain the part | m - s, that is, the use of the pipe symbol and the right arrow symbol which follow MonadState s m. -- frigidcode.com indicium.us ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120905/8b454fa2/attachment-0001.htm -- Message: 3 Date: Wed, 5 Sep 2012 09:46:45 -0700 From: KC kc1...@gmail.com Subject: [Haskell-beginners] Haskell seems setup for iterative numerics; i.e. a standard example is Newton's method where lazy evaluation ... To: haskell-cafe haskell-c...@haskell.org, beginners@haskell.org Message-ID: camlkxyk0d-vr75yrfn-xrnyw7447bnr11o1u4gagjpsikdq...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 separates control from computation. It seems as if Haskell would be better for iterative matrix methods rather than direct calculation. -- -- Regards, KC -- Message: 4 Date: Wed, 5 Sep 2012 13:10:52 -0700 From: KC kc1...@gmail.com Subject: Re: [Haskell-beginners] [Haskell-cafe] Haskell seems setup for iterative numerics; i.e. a standard example is Newton's method where lazy evaluation ... To: Carter Schonwald carter.schonw...@gmail.com Cc: beginners@haskell.org, haskell-cafe haskell-c...@haskell.org Message-ID: camlkxymrv9wyboo4orsgqhlqw-x_jm1ptcp6txmelqc43io...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 The REPA package/library doesn't have LU factorization, eigenvalues, etc. On Wed, Sep 5, 2012 at 12:59 PM, Carter Schonwald carter.schonw...@gmail.com wrote: Hello KC, you should check out the Repa library then and see how it works for you. Cheers -Carter On Wed, Sep 5, 2012 at 12:46 PM, KC kc1...@gmail.com wrote: separates control from computation. It seems as if Haskell would be better for iterative matrix methods rather than direct calculation. -- -- Regards, KC ___ Haskell-Cafe mailing list haskell-c...@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe --
Beginners Digest, Vol 51, Issue 10
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. splitAt and negative values (Stayvoid) 2. Re: splitAt and negative values (Brent Yorgey) 3. Re: splitAt and negative values (Stephen Tetley) 4. Re: splitAt and negative values (Tom Murphy) 5. Re: splitAt and negative values (Brandon Allbery) 6. Who discovered the fold operation? (Costello, Roger L.) 7. Re: Who discovered the fold operation? (Tony Morris) -- Message: 1 Date: Thu, 6 Sep 2012 21:24:13 +0400 From: Stayvoid stayv...@gmail.com Subject: [Haskell-beginners] splitAt and negative values To: beginners@haskell.org Message-ID: CAK5fS_GfyY7yog82droYJxY7fdi=ehcxvu+z8xg17y7dma3...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hello, Could you explain this behaviour? splitAt (-1) Foobar (,Foobar) splitAt (-100) Foobar (,Foobar) I don't understand why splitAt (-1) Foobar doesn't output this: (r, Fooba) or this: (, Fooba) How does it work? Python's list slicing looks similar, but results for negative values differ: a = Foobar a[:-1] 'Fooba' Thanks -- Message: 2 Date: Thu, 6 Sep 2012 17:12:47 -0400 From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-beginners] splitAt and negative values To: beginners@haskell.org Message-ID: 20120906211247.ga18...@seas.upenn.edu Content-Type: text/plain; charset=us-ascii On Thu, Sep 06, 2012 at 09:24:13PM +0400, Stayvoid wrote: Hello, Could you explain this behaviour? splitAt (-1) Foobar (,Foobar) splitAt (-100) Foobar (,Foobar) That is simply how splitAt is defined. It treats negative values as if they were 0. If you are looking for an explanation of *why* this behavior was chosen, it is probably because Haskell lists are really *singly-linked lists*, not arrays. Taking something off the end of a list takes O(n) time and requires making a copy of the entire list. So it wouldn't be a good idea to encourage it. If you really need this sort of functionality often then perhaps you should be using a different type, such as Data.Text, which has functions for doing things efficiently at the end of some text: http://hackage.haskell.org/package/text -Brent -- Message: 3 Date: Thu, 6 Sep 2012 22:14:09 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] splitAt and negative values To: Stayvoid stayv...@gmail.com Cc: beginners@haskell.org Message-ID: cab2tprdm3xd9o0a2d0s3wxctte+fwhhccbjzra0bti2tvrn...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 In Haskell positional list functions treat negative values as zero: take (-1) abc drop (-2) xyz xyz So, its idiomatic of splitAt to follow Haskell's precedent rather than Python's. -- Message: 4 Date: Thu, 6 Sep 2012 19:48:46 -0400 From: Tom Murphy amin...@gmail.com Subject: Re: [Haskell-beginners] splitAt and negative values To: Stayvoid stayv...@gmail.com Cc: beginners@haskell.org Message-ID: cao9q0tvrm9ur3_m2ngsjzd4tctwas31nigdwxa8ejyht2s_...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 One problem you might run into is: a = 4 b = 5 splitAt (a - b) [1..] If you don't know what a or b are beforehand, you might be opening up a can of uncomputable worms. Tom On Sep 6, 2012 1:25 PM, Stayvoid stayv...@gmail.com wrote: Hello, Could you explain this behaviour? splitAt (-1) Foobar (,Foobar) splitAt (-100) Foobar (,Foobar) I don't understand why splitAt (-1) Foobar doesn't output this: (r, Fooba) or this: (, Fooba) How does it work? Python's list slicing looks similar, but results for negative values differ: a = Foobar a[:-1] 'Fooba' Thanks ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120906/6770f82a/attachment-0001.htm -- Message: 5 Date: Thu, 6 Sep 2012 22:06:57 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] splitAt and negative values To: Stayvoid stayv...@gmail.com Cc: beginners@haskell.org Message-ID: CAKFCL4Vad0MRj73gkB98Vrp46N7JUFg8akNk8Z-CP+cGKV1=g...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Thu, Sep 6, 2012 at 1:24 PM, Stayvoid
Beginners Digest, Vol 51, Issue 14
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Data.Char: isAlpha vs. isLetter (Stayvoid) 2. Re: sometimes Haskell isn't what you want (Angelos Sphyris) 3. Re: Data.Char: isAlpha vs. isLetter (Brandon Allbery) 4. Re: sometimes Haskell isn't what you want (Nick Vanderweit) 5. Re: sometimes Haskell isn't what you want (Jay Sulzberger) 6. Who discovered map reduce? (Bryce) 7. Re: Who discovered map reduce? (Nick Vanderweit) 8. Re: Who discovered map reduce? (Rustom Mody) -- Message: 1 Date: Mon, 10 Sep 2012 23:09:20 +0400 From: Stayvoid stayv...@gmail.com Subject: [Haskell-beginners] Data.Char: isAlpha vs. isLetter To: beginners beginners@haskell.org Message-ID: CAK5fS_HdL+EKx45HmaujtCV2z=eer3obdpj15zu5nczxs-x...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi, What's the reason to have both isAlpha and isLetter? Looks like it's just an alias. I don't understand the purpose. Could you explain? Thanks -- Message: 2 Date: Mon, 10 Sep 2012 22:24:44 +0300 From: Angelos Sphyris knightofmathemat...@hotmail.com Subject: Re: [Haskell-beginners] sometimes Haskell isn't what you want To: dennis.rad...@gmail.com, beginners@haskell.org Message-ID: snt107-w90edf53f85dd9dc7ca35fa5...@phx.gbl Content-Type: text/plain; charset=iso-8859-7 Well, at least you now know that the language exists and you have some idea of where its associated resources (libraries, tutorials...) are located, so that you can take it up again if the need arises in the future... Angelos Date: Sun, 9 Sep 2012 01:10:14 -0700 From: dennis.rad...@gmail.com To: beginners@haskell.org Subject: [Haskell-beginners] sometimes Haskell isn't what you want Sadly, I've decided Haskell is not the right language for my current project. Python is better. I need to hack together data, and strict typing is getting in the way. Most of my algorithms are better served with imperative/mutable-data. I learned a lot about Haskell trying to do it, but my knowledge of the language is not quiet good enough and I feel like I'm fighting the language. Python is better. For now. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120910/efedfe73/attachment-0001.htm -- Message: 3 Date: Mon, 10 Sep 2012 15:31:26 -0400 From: Brandon Allbery allber...@gmail.com Subject: Re: [Haskell-beginners] Data.Char: isAlpha vs. isLetter To: Stayvoid stayv...@gmail.com Cc: beginners beginners@haskell.org Message-ID: cakfcl4v3q4pd3kwbr94ew5cgzhk+lsxxuic-vf1vz-b-pzt...@mail.gmail.com Content-Type: text/plain; charset=utf-8 On Mon, Sep 10, 2012 at 3:09 PM, Stayvoid stayv...@gmail.com wrote: What's the reason to have both isAlpha and isLetter? Probably an alias for backward compatibility; isAlpha is C-style ctype.h stuff, which was ASCII only, whereas isLetter is Unicode style. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120910/576612e2/attachment-0001.htm -- Message: 4 Date: Mon, 10 Sep 2012 14:16:02 -0700 (PDT) From: Nick Vanderweit nick.vanderw...@gmail.com Subject: Re: [Haskell-beginners] sometimes Haskell isn't what you want To: beginners@haskell.org Message-ID: 2776518.ja9fi27GRP@euler Content-Type: text/plain; charset=us-ascii I agree with this. Often it seems that Haskell takes longer to write, but I think this is because it makes you work harder than other languages before it compiles successfully. The tradeoff here is that you wind up with fewer runtime errors, which are more frustrating than compiler errors. A Haskell program is a proof of its own type. Writing proofs is a challenging task. Whether you want to incur this overhead is, of course, up to you as a programmer. Nick On Monday, September 10, 2012 03:28:45 PM damodar kulkarni wrote: ... strict typing is getting in the way When Haskell's strict typing seems to get in your way, chances are more that you are heading
Beginners Digest, Vol 51, Issue 15
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Data.Char: isAlpha vs. isLetter (Joey Hess) 2. Re: Data.Char: isAlpha vs. isLetter (Stayvoid) -- Message: 1 Date: Tue, 11 Sep 2012 01:49:19 -0400 From: Joey Hess j...@kitenet.net Subject: Re: [Haskell-beginners] Data.Char: isAlpha vs. isLetter To: beginners beginners@haskell.org Message-ID: 20120911054919.ga7...@gnu.kitenet.net Content-Type: text/plain; charset=us-ascii Brandon Allbery wrote: Probably an alias for backward compatibility; isAlpha is C-style ctype.h stuff, which was ASCII only, whereas isLetter is Unicode style. Prelude Data.Char all (\c - isLetter c == isAlpha c) [minBound..maxBound] True Whew! You had me worried my code had unicode bugs. isAlpha == isLetter -- see shy jo -- next part -- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 828 bytes Desc: Digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120911/ec32fa57/attachment-0001.pgp -- Message: 2 Date: Tue, 11 Sep 2012 09:52:05 +0400 From: Stayvoid stayv...@gmail.com Subject: Re: [Haskell-beginners] Data.Char: isAlpha vs. isLetter To: beginners beginners@haskell.org Message-ID: cak5fs_gqwj49hcmzn6g2skn5eo4rsh7fchmd8oyvadmjsbf...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Probably an alias for backward compatibility; isAlpha is C-style ctype.h stuff, which was ASCII only, whereas isLetter is Unicode style. Both Haskell functions support non-ASCII chars. Does it refute your assumption? Thanks -- ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 51, Issue 15 *
Beginners Digest, Vol 51, Issue 16
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: sometimes Haskell isn't what you want (Dennis Raddle) 2. Re: sometimes Haskell isn't what you want (Anindya Mozumdar) 3. Re: Data.Char: isAlpha vs. isLetter (Brandon Allbery) 4. Re: Data.Char: isAlpha vs. isLetter (Brandon Allbery) 5. Data.Map: fromList (Stayvoid) 6. Re: Data.Map: fromList (Brandon Allbery) -- Message: 1 Date: Tue, 11 Sep 2012 05:16:15 -0700 From: Dennis Raddle dennis.rad...@gmail.com Subject: Re: [Haskell-beginners] sometimes Haskell isn't what you want To: Jay Sulzberger j...@panix.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAKxLvor__0rv6rOfEB77oL4mgv11Pz-=ka8fzcutfaqc2e7...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 I went briefly to Python but guess what? I I U-turned right back to Haskell. Because there is nothing like the consistent documentation and well-thought-out libraries of Haskell. There is nothing else like the help from #haskell or this list. I used to program in Python. I went back to it for one day (yesterday) and that was enough to make me realize how unpleasant its inconsistencies, inconsistent documentation, awkwardnesses, etc. Maybe Haskell will make me think harder but at least the whole language and supporting documentation and the whole community has got my back. Haskell is a gift and I'm not throwing it away. Yay! On Mon, Sep 10, 2012 at 2:23 PM, Jay Sulzberger j...@panix.com wrote: On Sun, 9 Sep 2012, Dennis Raddle dennis.rad...@gmail.com wrote: Sadly, I've decided Haskell is not the right language for my current project. Python is better. I need to hack together data, and strict typing is getting in the way. Most of my algorithms are better served with imperative/mutable-data. I learned a lot about Haskell trying to do it, but my knowledge of the language is not quiet good enough and I feel like I'm fighting the language. Python is better. For now. I always recommend Scheme. It is like Haskell in one respect: The Scheme Tribes keep the Ritual and the Law of Lambda. Scheme is different from Haskell in two respects: We Lispers do all our coding under the Great Functor, the Great Functor from Code to Objects in the Lisp World. For most Scheme systems, the Type Sub-System calculates less at compile time. Robert Harper has a new textbook available at http://www.cs.cmu.edu/~rwh/**plbook/book.pdfhttp://www.cs.cmu.edu/~rwh/plbook/book.pdf and here is a useful notice of the book http://blog.ezyang.com/2012/**08/practical-foundations-for-** programming-languages/http://blog.ezyang.com/2012/08/practical-foundations-for-programming-languages/ ad missing the Great Functor: See remarks on symbols in the section 32.3 on page 321, and the discussion of observational equivalence in section 47.1 on page 498. A Lisper reading these sections might say Ah, the Great Functor is worthy of study by New Type Theorists too. We Lispers consider a symbol to be a symbol first, and nothing else until you pass across one or more functors, and then the symbol might become many different things.. ad dynamic typing vs static typing: Professor Harper's blog post http://existentialtype.**wordpress.com/2011/03/19/** dynamic-languages-are-static-**languages/http://existentialtype.wordpress.com/2011/03/19/dynamic-languages-are-static-languages/ deals with this. I think the claim made, that dynamic typing is a special case of static typing, is, when sympathetically read, right. oo--JS. __**_ Beginners mailing list Beginners@haskell.org http://www.haskell.org/**mailman/listinfo/beginnershttp://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120911/b360c162/attachment-0001.htm -- Message: 2 Date: Tue, 11 Sep 2012 19:04:14 +0530 From: Anindya Mozumdar anindya.lugb...@gmail.com Subject: Re: [Haskell-beginners] sometimes Haskell isn't what you want To: Dennis Raddle dennis.rad...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CADUR+2boDwjv25eFM_9Kbo_XQ4uUMn=syfjvvnuan7tgnb4...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I went back to it for one day (yesterday) and that was enough to make me realize how unpleasant its inconsistencies,
Beginners Digest, Vol 51, Issue 17
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Today's Topics:
1. Reactive Banana Data Structures Sanity Check (Michael Litchard)
2. Playing and combining audio files (Tobias)
3. Re: sometimes Haskell isn't what you want (Darren Grant)
4. Re: sometimes Haskell isn't what you want (Mike Meyer)
5. Re: sometimes Haskell isn't what you want (Darren Grant)
6. Re: sometimes Haskell isn't what you want (Jay Sulzberger)
7. Re: sometimes Haskell isn't what you want (Michael Carpenter)
8. Re: Playing and combining audio files (Tom Murphy)
--
Message: 1
Date: Tue, 11 Sep 2012 11:38:17 -0700
From: Michael Litchard mich...@schmong.org
Subject: [Haskell-beginners] Reactive Banana Data Structures Sanity
Check
To: beginners@haskell.org
Message-ID:
caezekyp4gbaboysbu0eefbmqnv_3ywh3lxnsxd9hpfd2gve...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
I'm making an implementation of Grand Theft Wumpus using
reactive-banana. I'm using the slot machine example to work from.
For now, I'm just building a simple graph where a Player can move from
Node to Node. I'm not sure I have the Data Structures right, so I
wanted to run it by the community. I'm conceptualizing each Node (a
Street) and the Player as a Behavior. I reason that since the Graph
won't change, just the values inside a Node, I can update any Node as
needed, instead of creating a new Graph whenever a value in a Node
changes. It seems though, as I scale up, I'd end up with a big union
of Behaviors. Does it make sense to describe each Node as a Behavior?
Even though I'm starting simply, I intend to write a complete
implementiation.
http://nostarch.com/download/Lisp08.pdf
data StreetName = Baker
| Main
| Atlantic
| Baltic
| Connecticut
deriving (Enum,Bounded,Show)
type Player t = Behavior t Player_
type Street t = Behavior t Street_
data Player_ = Player {location :: StreetName } deriving Show
data Street_ = Street_ {sName :: StreetName
,player :: Maybe Player_
} deriving Show
data GameEvent = MovePlayer Street
| Look
does that look okay so far?
--
Message: 2
Date: Tue, 11 Sep 2012 21:12:45 +0200
From: Tobias tobn...@freenet.de
Subject: [Haskell-beginners] Playing and combining audio files
To: beginners@haskell.org
Message-ID: 504f8d2d.5040...@freenet.de
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hello,
I'm searching for a library with which I can process audio files (.wav
or .mp3). All I need is functions with which I can
- play audio files
- concat several audio files to one audio file
Can you suggest a library for this task? I looked through
http://hackage.haskell.org/packages/archive/pkg-list.html#cat:sound but
I didn't manage to find ways to do this respectively sample code for this.
Any hints are welcome- thanks,
Tobias
--
Message: 3
Date: Tue, 11 Sep 2012 13:21:11 -0700
From: Darren Grant therealklu...@gmail.com
Subject: Re: [Haskell-beginners] sometimes Haskell isn't what you want
To: Anindya Mozumdar anindya.lugb...@gmail.com
Cc: Haskell Beginners beginners@haskell.org
Message-ID:
ca+jd6sghtef4ypzq0cunkqyuh8_h--z63cgz-0gndx5ebp1...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
Just adding another perspective: I developed the AI for a complex
turn-based strategy game in C++. By the end of the process I found
that I was not only continually repeating myself due to the language
syntax because I needed a *lot* of specialized list manipulations, but
I was also effectively composing pure functions.
This made me think that it could be much more effective to develop AI
in a functional language. There's no way I could do this with Haskell
presently as I am still struggling to approach all problems from the
FP perspective first, but I do think there is the potential.
Cheers,
Darren
On Tue, Sep 11, 2012 at 6:34 AM, Anindya Mozumdar
anindya.lugb...@gmail.com wrote:
I went back to it
for one day (yesterday) and that was enough to make me realize how
unpleasant its inconsistencies, inconsistent documentation, awkwardnesses,
etc.
Haskell is a gift and I'm not throwing it away.
Luckily this is a small list, otherwise a flame war would have started by now.
Personally, I learnt the basics of Haskell in the year 2000 in
college. I am
Beginners Digest, Vol 51, Issue 19
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than Re: Contents of Beginners digest...
Today's Topics:
1. Re: Question about time consume when calculate prime numbers
(Yi Cheng)
2. Re: Question about time consume when calculate prime numbers
(Lorenzo Bolla)
3. Re: Question about time consume when calculate prime numbers
(Yi Cheng)
--
Message: 1
Date: Wed, 12 Sep 2012 20:17:54 +0800
From: Yi Cheng chengyi...@gmail.com
Subject: Re: [Haskell-beginners] Question about time consume when
calculate prime numbers
To: Lorenzo Bolla lbo...@gmail.com
Cc: beginners@haskell.org
Message-ID:
caek-nmenqhk4ww6kdi-6dwwarrfzz3nqxx0rgknu0l7sehe...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
Thanks for answering my question, but I'm still confused by some details.
I don't quite agree with you that Eratosthenes algorithm must be
implemented with a complexity of O(n^2) in space. When the n is used to
calculate the primes below it, it can be implemented in space complexity
O(n). For example, in languages, like C/C++, we can allocate a array. So I
think the the complexity of O(n^2) in space you mentioned, is the
complexity of the beautiful code. So here's the question, can
Eratosthenes algorithm be implemented in a more gentle way?
Then I think maybe there is a more beautiful and practical way to implement
it.
One method of mine is trying to judge whether a number is a prime just by
the primes less than it, such as if the greatest common divisor of the
number and the product of the primes less than it equals to 1. But the
product of the primes is too large.
So I wander if there is a concise method to solve the problem with a faster
method. In my C++ version, the Eratosthenes is implemented in linear space
complexity, and optimize in filtering the numbers which can be divided by a
prime. This code is faster than the original algorithm implemented by me(It
was also implemented it in C++, and slower than the following code).
I know, when writing Haskell code, it would be better to forget some
experience in command-line language, but I want to know whether there is a
faster method to solve the problem.
Thank you.
Yi. Cheng
The code in my c++ version.
#include iostream
using namespace std;
int main(){
int p[200] = {0};
long sum = 0;
int f = 1;
for(long i=2; i = 200; ++i){
if(p[i] == 0){
sum += i;
for(long j = i * i; j 200; j += i)
p[j] = 1;
}
}
coutsumendl;
return 0;
}
On Wed, Sep 12, 2012 at 5:26 PM, Lorenzo Bolla lbo...@gmail.com wrote:
On Wed, Sep 12, 2012 at 9:06 AM, Yi Cheng chengyi...@gmail.com wrote:
Recently, I'm trying to solve some problems in project euler using
haskell. When it came to problem 10, calculating the sum of all primes
below 2000, I try to write a program which can generate primes.
In my memory Eratosthenes is faster than just whether a number can be
divided by the number less then the square root of it.
Firstly, I wrote the following programs:
module Main where
isPrime x = isPrime' 3 x (round . sqrt. fromIntegral $ x)
isPrime' d target maxd
| d maxd = True
| mod target d == 0 = False
| otherwise = isPrime' (d + 2) target maxd
main = print $ (sum (filter isPrime [3,5..200]) + 2)
And it consume about 11s in my computer.
Then, I tried to figure out how to solve the problem by Eratosthenes, but
failed. Later, I find a program implemented by others, meeting my purpose
and I've used it to solve the problem:
primes :: [Int]
primes = primes' [2..]
primes' :: [Int] - [Int]
primes' [] = []
primes' (n:ns) = n : primes' (filter (\v - v `mod` n /= 0) ns)
solve x = sum $ primes' [2..x]
main = print $ solve 200
Well, although the code is beautiful, it is slow. Even waiting for a
minute, no answer was printed.
In C version, Eratosthenes is faster than the method implemented in my
earlier code, which only consume 0.3s(the earlier method consume 1.6s).
So I want to know, why Eratosthenes implemented in Haskell is slow than
the ugly code implemented by me.
Could anyone tell me?
Eratosthenes's complexity is O(n^2) (both space and time), whereas the
ugly one has a sub-quadratic running complexity and linear in space.
Try to profile them:
$ ghc -O2 --make -prof -auto-all filename
$ ./primes +RTS -p -hc
$ hp2ps primes.hp
You'll see that most of the time is spent allocating space which is never
released.
You could play a bit with
Beginners Digest, Vol 51, Issue 20
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Haskell for Android (Miroslav Karpis) 2. Re: Haskell for Android (Henk-Jan van Tuyl) 3. Re: Question about time consume when calculate prime numbers (Fletcher Stump Smith) 4. cyclic imports (Christopher Howard) 5. Re: cyclic imports (Chadda? Fouch?) -- Message: 1 Date: Wed, 12 Sep 2012 19:21:28 +0200 From: Miroslav Karpis miroslav.kar...@gmail.com Subject: [Haskell-beginners] Haskell for Android To: Beginners@haskell.org Message-ID: 462f4004-91b0-42aa-a947-251be3fc9...@gmail.com Content-Type: text/plain; charset=windows-1252 Hi haskellers, please can you help me with this? I read several posts about it, but unfortunately it is still not clear. What is (if there is) the most straight way to port haskell code to android? Translate haskell to c or javascript? Not sure how debugging will work this way?. ? thanks, m. -- Message: 2 Date: Wed, 12 Sep 2012 22:30:57 +0200 From: Henk-Jan van Tuyl hjgt...@chello.nl Subject: Re: [Haskell-beginners] Haskell for Android To: Beginners@haskell.org, Miroslav Karpis miroslav.kar...@gmail.com Message-ID: op.wkjhxvl5pz0...@zen5.arnhem.chello.nl Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes On Wed, 12 Sep 2012 19:21:28 +0200, Miroslav Karpis miroslav.kar...@gmail.com wrote: Hi haskellers, please can you help me with this? I read several posts about it, but unfortunately it is still not clear. What is (if there is) the most straight way to port haskell code to android? There is a HaskellWiki page for Android[0] with some interesting links. This article is a stub; anyone who is an expert in this area, please add more info. Regards, Henk-Jan van Tuyl [0] http://www.haskell.org/haskellwiki/Android -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming -- -- Message: 3 Date: Wed, 12 Sep 2012 15:32:13 -0700 From: Fletcher Stump Smith fletcher...@gmail.com Subject: Re: [Haskell-beginners] Question about time consume when calculate prime numbers To: Yi Cheng chengyi...@gmail.com Cc: beginners@haskell.org Message-ID: CAPEBXRzXt+LNGHDSgWBgpniS34wZxt+HZobA=anox9krwht...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 You might also be interested in this paper: www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf . I thought it was a good analysis/ On Wed, Sep 12, 2012 at 8:53 AM, Yi Cheng chengyi...@gmail.com wrote: Thank you, very much. It's exactly the thing I want to know. Yi. Cheng On Wed, Sep 12, 2012 at 8:41 PM, Lorenzo Bolla lbo...@gmail.com wrote: On Wed, Sep 12, 2012 at 1:17 PM, Yi Cheng chengyi...@gmail.com wrote: Thanks for answering my question, but I'm still confused by some details. I don't quite agree with you that Eratosthenes algorithm must be implemented with a complexity of O(n^2) in space. When the n is used to calculate the primes below it, it can be implemented in space complexity O(n). For example, in languages, like C/C++, we can allocate a array. So I think the the complexity of O(n^2) in space you mentioned, is the complexity of the beautiful code. So here's the question, can Eratosthenes algorithm be implemented in a more gentle way? Correct: I referred to your implementation. See here (http://www.haskell.org/haskellwiki/Prime_numbers#Sieve_of_Eratosthenes) for many different (and more efficient) implementations of Eratosthenes. Then I think maybe there is a more beautiful and practical way to implement it. One method of mine is trying to judge whether a number is a prime just by the primes less than it, such as if the greatest common divisor of the number and the product of the primes less than it equals to 1. But the product of the primes is too large. So I wander if there is a concise method to solve the problem with a faster method. In my C++ version, the Eratosthenes is implemented in linear space complexity, and optimize in filtering the numbers which can be divided by a prime. This code is faster than the original algorithm implemented by me(It was also implemented it in C++, and slower than the following code). I know, when writing Haskell code, it would be better to forget some experience in command-line language, but I want to know whether there is a faster method to solve the problem. Thank you. Yi. Cheng The code in my c++ version.
Beginners Digest, Vol 51, Issue 22
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When replying, please edit your Subject line so it is more specific
than Re: Contents of Beginners digest...
Today's Topics:
1. Re: Reactive Banana Data Structures Sanity Check
(Heinrich Apfelmus)
2. Comfortable handling of module hierarchies (Christopher Howard)
3. Algorithmic Advances by Discovering Patterns in Functions
(Costello, Roger L.)
--
Message: 1
Date: Fri, 14 Sep 2012 15:45:49 +0200
From: Heinrich Apfelmus apfel...@quantentunnel.de
Subject: Re: [Haskell-beginners] Reactive Banana Data Structures
Sanity Check
To: beginners@haskell.org
Message-ID: k2vcec$du1$1...@ger.gmane.org
Content-Type: text/plain; charset=UTF-8; format=flowed
Michael Litchard wrote:
I'm making an implementation of Grand Theft Wumpus using
reactive-banana. I'm using the slot machine example to work from.
For now, I'm just building a simple graph where a Player can move from
Node to Node. I'm not sure I have the Data Structures right, so I
wanted to run it by the community. I'm conceptualizing each Node (a
Street) and the Player as a Behavior. I reason that since the Graph
won't change, just the values inside a Node, I can update any Node as
needed, instead of creating a new Graph whenever a value in a Node
changes. It seems though, as I scale up, I'd end up with a big union
of Behaviors. Does it make sense to describe each Node as a Behavior?
Even though I'm starting simply, I intend to write a complete
implementiation.
http://nostarch.com/download/Lisp08.pdf
data StreetName = [...]
type Player t = Behavior t Player_
type Street t = Behavior t Street_
data Player_ = Player {location :: StreetName } deriving Show
data Street_ = Street_ {sName :: StreetName
,player :: Maybe Player_
} deriving Show
data GameEvent = MovePlayer Street
| Look
does that look okay so far?
That's hard to say. It certainly doesn't look wrong, but whether it's a
good idea or not depends on what you will do later.
My process for programming with Functional Reactive Programming (FRP) is
usually this:
* What is the end product, i.e. the thing that users ultimately
interact with? In your case, it's probably the drawing of a map of the city.
* Does the end product vary in time? Yes? Then it's going to be a
Behavior City , i.e. a data structure that describes the evolution of
the city in time.
* How does the city evolve in time? Here I start to think of the events
and other behaviors that I use to define the behavior, for instance by
writing
bcity :: Behavior City
bcity = stepper ... -- step function from events
or
bcity = (++) $ bsuburbs * bcenter -- combine other behaviors
and so on.
The process is a bit like thinking as a physicist in god-mode: for each
object in my little universe, I specify where it should be at any
particular time, like 5 o'clock.
That said, I found it useful to decouple the interaction of individual
parts -- city, node, player -- from their time evolution. Have a look at
the Asteroids.hs example
http://www.haskell.org/haskellwiki/Reactive-banana/Examples#asteroids
The bottom part of the source contains function like advanceRocks or
collide that specify more complicated interactions between different
objects. The FRP part of the source file just specifies *when* these
interactions take place, i.e. advanceRocks happens when etick
happens while the player moves when eleft or eright happen.
In other words, my rule of thumb is
How does it happen? = ordinary functions
When does it happen? = events and behaviors
In particular, you can write your Wumpus game logic by asking the how
questions first and only then ask the when questions. Thus, I would
rename Player_ to Player for the how part and simply use Behavior
t Player for the fairly small when part.
Hope that helps.
Best regards,
Heinrich Apfelmus
--
http://apfelmus.nfshost.com
--
Message: 2
Date: Fri, 14 Sep 2012 17:23:45 -0800
From: Christopher Howard christopher.how...@frigidcode.com
Subject: [Haskell-beginners] Comfortable handling of module
hierarchies
To: Haskell Beginners beginners@haskell.org
Message-ID: 5053d8a1.7030...@frigidcode.com
Content-Type: text/plain; charset=iso-8859-1
So, let's say I've got this hierarchy of modules:
Plant
`-- Vegetable
|`-- Celery
|`-- Lettuce
`-- Fruit
`-- Raspberry
`-- Apple
What I would like to be able to do is import and
Beginners Digest, Vol 51, Issue 23
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Comfortable handling of module hierarchies (Karl Voelker) 2. FRP (Christopher Howard) 3. Re: FRP (Ertugrul S?ylemez) 4. Re: FRP (Ertugrul S?ylemez) 5. Re: FRP (Christopher Howard) 6. Re: FRP (Ertugrul S?ylemez) -- Message: 1 Date: Sat, 15 Sep 2012 09:00:55 -0700 From: Karl Voelker ktvoel...@gmail.com Subject: Re: [Haskell-beginners] Comfortable handling of module hierarchies To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAFfow0zM4QsP_3m_8Qx8JrCxa3-FXDzi89H4XoWXzP8uLs=m...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 On Fri, Sep 14, 2012 at 6:23 PM, Christopher Howard christopher.how...@frigidcode.com wrote: import qualified Plant as P P.Fruit.Raspberry.jam Short answer: P.Fruit.Raspberry.jam would work if you said: import qualified Plant.Fruit.Raspberry as P.Fruit.Raspberry Long answer: You can't have exactly what you want because the Haskell module namespace isn't exactly heirarchical. Here's an excerpt from the Haskell 98 report [1]: The name-space for modules themselves is flat, with each module being associated with a unique module name (which are Haskell identifiers beginning with a capital letter; i.e. modid). Notice that this doesn't allow for dots in module names. A commonly-provided language extension allowed dots in module names, and compilers took these dots as a signal to look for a module's source at a particular place in the directory tree, but the semantics of the language didn't have a heirarchy of modules. Things haven't changed much in Haskell 2010, other than the existing use of dots being formalized [2]: Module names can be thought of as being arranged in a hierarchy in which appending a new component creates a child of the original module name. For example, the module Control.Monad.ST is a child of the Control.Monad sub-hierarchy. This is purely a convention, however, and not part of the language definition; in this report a modid is treated as a single identifier occupying a flat namespace. In your code snippet, P.Fruit.Raspberry doesn't work because although P refers to the same module as Plant, there isn't anything inside P (or Plant) called Fruit.Raspberry. -Karl [1] http://www.haskell.org/onlinereport/modules.html [2] http://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-980005 -- Message: 2 Date: Sat, 15 Sep 2012 22:15:04 -0800 From: Christopher Howard christopher.how...@frigidcode.com Subject: [Haskell-beginners] FRP To: Haskell Beginners beginners@haskell.org Message-ID: 50556e68.1000...@frigidcode.com Content-Type: text/plain; charset=iso-8859-1 Hi. I'm trying to understand what Functional Reactive Programming is, or, more properly, what distinguishes it from regular functional programming, and what it would look like if I were to program in a FRP Style, i.e., without some mysterious FRP module hiding the details. After reading a bunch of links and even looking at some source code I'm still not clear on this. If I program in an event-based style, and have data structures updating over time, with some data structures dependent on others for their values, and I use a functional language, is that FRP? Or is there some essential element I'm missing here? -- frigidcode.com indicium.us -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 551 bytes Desc: OpenPGP digital signature URL: http://www.haskell.org/pipermail/beginners/attachments/20120915/944bf65e/attachment-0001.pgp -- Message: 3 Date: Sun, 16 Sep 2012 09:16:19 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] FRP To: beginners@haskell.org Message-ID: 20120916091619.44ace...@tritium.streitmacht.eu Content-Type: text/plain; charset=us-ascii Christopher Howard christopher.how...@frigidcode.com wrote: Hi. I'm trying to understand what Functional Reactive Programming is, or, more properly, what distinguishes it from regular functional programming, and what it would look like if I were to program in a FRP Style, i.e., without some mysterious FRP module hiding the details. After reading a bunch of links and even looking at some source code I'm still not clear on this. If I program in an event-based style, and have data
Beginners Digest, Vol 51, Issue 24
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Comfortable handling of module hierarchies (damodar kulkarni) 2. Re: FRP (Henk-Jan van Tuyl) 3. Re: FRP (Ertugrul S?ylemez) 4. Re: Comfortable handling of module hierarchies (Edward Z. Yang) 5. Re: Comfortable handling of module hierarchies (damodar kulkarni) 6. Re: Comfortable handling of module hierarchies (Brandon Allbery) 7. Re: FRP (Heinrich Apfelmus) -- Message: 1 Date: Sun, 16 Sep 2012 16:07:41 +0530 From: damodar kulkarni kdamodar2...@gmail.com Subject: Re: [Haskell-beginners] Comfortable handling of module hierarchies To: Karl Voelker ktvoel...@gmail.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAD5HsyoeY0_RSGYC7SzTB=R=onngrerw+wc3vdnpmeskwvo...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Do you know any document pointing out the rationale behind this decision about modules taken by the Haskell designers? Thanks. -Damodar On Sat, Sep 15, 2012 at 9:30 PM, Karl Voelker ktvoel...@gmail.com wrote: On Fri, Sep 14, 2012 at 6:23 PM, Christopher Howard christopher.how...@frigidcode.com wrote: import qualified Plant as P P.Fruit.Raspberry.jam Short answer: P.Fruit.Raspberry.jam would work if you said: import qualified Plant.Fruit.Raspberry as P.Fruit.Raspberry Long answer: You can't have exactly what you want because the Haskell module namespace isn't exactly heirarchical. Here's an excerpt from the Haskell 98 report [1]: The name-space for modules themselves is flat, with each module being associated with a unique module name (which are Haskell identifiers beginning with a capital letter; i.e. modid). Notice that this doesn't allow for dots in module names. A commonly-provided language extension allowed dots in module names, and compilers took these dots as a signal to look for a module's source at a particular place in the directory tree, but the semantics of the language didn't have a heirarchy of modules. Things haven't changed much in Haskell 2010, other than the existing use of dots being formalized [2]: Module names can be thought of as being arranged in a hierarchy in which appending a new component creates a child of the original module name. For example, the module Control.Monad.ST is a child of the Control.Monad sub-hierarchy. This is purely a convention, however, and not part of the language definition; in this report a modid is treated as a single identifier occupying a flat namespace. In your code snippet, P.Fruit.Raspberry doesn't work because although P refers to the same module as Plant, there isn't anything inside P (or Plant) called Fruit.Raspberry. -Karl [1] http://www.haskell.org/onlinereport/modules.html [2] http://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-980005 ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- next part -- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20120916/bb143a37/attachment-0001.htm -- Message: 2 Date: Sun, 16 Sep 2012 13:05:23 +0200 From: Henk-Jan van Tuyl hjgt...@chello.nl Subject: Re: [Haskell-beginners] FRP To: beginners@haskell.org, Ertugrul S?ylemez e...@ertes.de Message-ID: op.wkp6e9mvpz0...@zen5.arnhem.chello.nl Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes Hello Ertugrul, Can I use your explanation for the HaskellWiki FRP page[0]? Regards, Henk-Jan van Tuyl [0] http://www.haskell.org/haskellwiki/Functional_Reactive_Programming -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming -- -- Message: 3 Date: Sun, 16 Sep 2012 13:21:57 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] FRP To: beginners@haskell.org Message-ID: 20120916132157.79af1...@tritium.streitmacht.eu Content-Type: text/plain; charset=us-ascii Henk-Jan van Tuyl hjgt...@chello.nl wrote: Can I use your explanation for the HaskellWiki FRP page[0]? Sure. Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size:
Beginners Digest, Vol 51, Issue 25
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Algorithmic Advances by Discovering Patterns in Functions (Darren Grant) 2. trouble with install SDL? (Gregory Guthrie) -- Message: 1 Date: Sun, 16 Sep 2012 11:11:34 -0700 From: Darren Grant therealklu...@gmail.com Subject: Re: [Haskell-beginners] Algorithmic Advances by Discovering Patterns in Functions To: beginners@haskell.org beginners@haskell.org Message-ID: ca+jd6sit+kiisecnb3kuzdqfct8ydumgepfhs_7ky6b9+_k...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Thanks for this! On Sat, Sep 15, 2012 at 1:36 AM, Costello, Roger L. coste...@mitre.org wrote: Hi Folks, This is a story about discovery. It is a story about advancing the state-of-the-art by discovering patterns in functions. Scientists look for recurring patterns in nature. Once a pattern is discovered, its essential ingredients are identified and formalized into a law or mathematical equation. Discovery of a pattern is important and those individuals who make such discoveries are rightfully acknowledged in our annals of science. Scientists are not the only ones who look for recurring patterns, so do functional programmers. Once a pattern is discovered, its essential ingredients are identified and formalized into a function. That function may then become widely adopted by the programming community, thus elevating the programming community to a new level of capability. The following is a fantastic example of discovering a pattern in multiple functions, discerning the essential ingredients of the pattern, and replacing the multiple functions with a single superior function. The example is from Richard Bird's book, Introduction to Functional Programming using Haskell. Before looking at the example let's introduce an important concept in functional programming: partial function application. A function that takes two arguments may be rewritten as a function that takes one argument and returns a function. The function returned also takes one argument. For example, consider the min function which returns the minimum of two integers: min 2 3 -- returns 2 Notice that min is a function that takes two arguments. Suppose min is given only one argument: min 2 [Definition: When fewer arguments are given to a function than it can accept it is called partial application of the function. That is, the function is partially applied.] min 2 is a function. It takes one argument. It returns the minimum of the argument and 2. For example: (min 2) 3 -- returns 2 To see this more starkly, let's assign g to be the function min 2: let g = min 2 g is now a function that takes one argument and returns the minimum of the argument and 2: g 3 -- returns 2 Let's take a second example: the addition operator (+) is a function and it takes two arguments. For example: 2 + 3 -- returns 5 To make it more obvious that (+) is a function, here is the same example in prefix notation: (+) 2 3 -- returns 5 Suppose we provide (+) only one argument: (+) 2 That is a partial application of the (+) function. (+) 2 is a function. It takes one argument. It returns the sum of the argument and 2. For example: ((+) 2) 3 -- returns 5 We can succinctly express (+) 2 as: (+2) Thus, (+2) 3 -- returns 5 Okay, now we are ready to embark on our journey of discovery. We will examine three functions and find their common pattern. The functions process values from this recursive data type: data Nat = Zero | Succ Nat Here are some examples of Nat values: Zero, Succ Zero, Succ (Succ Zero), Succ (Succ (Succ Zero)), ... The following functions perform addition, multiplication, and exponentiation on Nat values. Examine the three functions. Can you discern a pattern? -- Addition of Nat values: m + Zero = m m + Succ n = Succ(m + n) -- Multiplication of Nat values: m * Zero = Zero m * Succ n = (m * n) + m -- Exponentiation of Nat values: m ** Zero = Succ Zero m ** Succ n = (m ** n) * m For each function the right-hand operand is either Zero or Succ n: (+m) Zero (+m) Succ n (*m) Zero (*m) Succ n (**m) Zero (**m) Succ n So abstractly there is a function f that takes as argument either Zero or Succ n: f Zero f Succ n Given Zero as the argument, each function immediately returns a value: (+m) Zero = m (*m) Zero
Beginners Digest, Vol 51, Issue 26
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: trouble with install SDL? (Stephen Tetley) 2. Sending mail via SMTP (Salil Wadnerkar) 3. Re: Algorithmic Advances by Discovering Patterns in Functions (Kim-Ee Yeoh) -- Message: 1 Date: Mon, 17 Sep 2012 17:49:52 +0100 From: Stephen Tetley stephen.tet...@gmail.com Subject: Re: [Haskell-beginners] trouble with install SDL? To: Gregory Guthrie guth...@mum.edu Cc: beginners@haskell.org beginners@haskell.org Message-ID: cab2tprastwzz1gwm1j2qy2+4ayjxshchai9x2nfrrvzetkn...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi Gergory You want to build the binding under MinGW / SYS using the development headers and libraries from libsdl.org packaged as SDL-devel-1.2.15-mingw32.tar.gz (or a later version if there is one). SDL-devel-1.12.15-mingw32.tar.gz installs easily after unpacking (I believe it ships mostly binary components rather than builds anything much from source). To build the Haskell binding you want to tell Cabal to use these libs: Extra-Libraries: SDL.dll SDLmain Additionally point to the extra devel and lib dirs - for me with a vanilla install of SDL-devel-1.12.15-mingw32.tar.gz they located in these directories: Include-Dirs: C:\msys\1.0\include\SDL SDL includes the toplevel header SDL.h, plus others. Extra-Lib-Dirs: C:\msys\1.0\lib which should contain libSDL.dll.a, libSDL.la, and libSDLmain.a I modified my local SDL.cabal file to include these changes (otherwise I'd likely forget them if I needed to rebuild), but you should be able to pass them as options to runhaskell Set.lhs configure Regards Stephen -- Message: 2 Date: Tue, 18 Sep 2012 07:32:45 +0800 From: Salil Wadnerkar rohsh...@gmail.com Subject: [Haskell-beginners] Sending mail via SMTP To: beginners@haskell.org Message-ID: cahrrg0ovv8-+zsicn75fhuu6t3r6c8a4xwykaau24er7wb4...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi, Does anybody know of any good libraries I can use to send a mail via google's SMTP? I found SMTPClient and HaskellNet. The former does not support TLS and the latter does not seem to have examples for using TLS to send an email via SMTP. Did anybody manage to do that? Thanks Salil -- Message: 3 Date: Tue, 18 Sep 2012 15:56:12 +0700 From: Kim-Ee Yeoh k...@atamo.com Subject: Re: [Haskell-beginners] Algorithmic Advances by Discovering Patterns in Functions To: Costello, Roger L. coste...@mitre.org Cc: beginners@haskell.org beginners@haskell.org Message-ID: capy+zdqwrtbm8eyq7dr1drlbhg3uf5wfad5lrnj7kv18uaz...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Roger, Scientists look for recurring patterns in nature. Once a pattern is discovered, its essential ingredients are identified and formalized into a law or mathematical equation. You could think of lambda calculus as a general language for formalizing and applying patterns. Squint enough and pinning down a pattern starts to look like lambda abstraction; using the pattern, function application. Here is some intuition on why it is called the fold function: Imagine folding a towel. Generally we don't look for insight in the layperson meaning of technical terminology. Sure, folding a list is intuitively like folding a long strip of paper. But folds also apply to trees and even gnarlier datatypes, and there intuition loses steam. Sometimes it's better to internally alpha-rename to a fresh variable to avoid being misled. The meaning lies in the *usage* of the term, so in a way it's not really in English after all. We saw that the fold function can be defined for the Nat data type. In fact, a suitable fold function can be defined for every recursive data type. How would you define a fold for data S a = S (a - Bool) ? -- Kim-Ee On Sat, Sep 15, 2012 at 3:36 PM, Costello, Roger L. coste...@mitre.org wrote: Hi Folks, This is a story about discovery. It is a story about advancing the state-of-the-art by discovering patterns in functions. Scientists look for recurring patterns in nature. Once a pattern is discovered, its essential ingredients are identified and formalized into a law or mathematical equation. Discovery of a pattern is important and those individuals who make such discoveries are rightfully acknowledged in our annals of science. Scientists are not the only ones who look for recurring patterns, so
Beginners Digest, Vol 51, Issue 27
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: Sending mail via SMTP (Anindya Mozumdar) 2. Re: Sending mail via SMTP (Salil Wadnerkar) 3. Re: Sending mail via SMTP (Robert Wills) 4. Re: Sending mail via SMTP (Tim Perry) 5. Re: FRP (Christopher Howard) 6. Re: Algorithmic Advances by Discovering Patterns in Functions (Jay Sulzberger) 7. Re: FRP (Darren Grant) -- Message: 1 Date: Tue, 18 Sep 2012 20:10:30 +0530 From: Anindya Mozumdar anindya.lugb...@gmail.com Subject: Re: [Haskell-beginners] Sending mail via SMTP To: Salil Wadnerkar rohsh...@gmail.com Cc: beginners@haskell.org Message-ID: cadur+2yhk4fbplguo5x01qtwy2aaxaf4fncyyx4wcnwvjqu...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Does anybody know of any good libraries I can use to send a mail via google's SMTP? I found SMTPClient and HaskellNet. The former does not support TLS and the latter does not seem to have examples for using TLS to send an email via SMTP. Did anybody manage to do that? A fellow beginner, so I don't have indepth knowledge of the subject. But can this help - http://stackoverflow.com/questions/8036680/haskell-smtp-over-ssl http://www.haskell.org/pipermail/beginners/2012-July/010190.html -- Message: 2 Date: Tue, 18 Sep 2012 23:08:50 +0800 From: Salil Wadnerkar rohsh...@gmail.com Subject: Re: [Haskell-beginners] Sending mail via SMTP To: Anindya Mozumdar anindya.lugb...@gmail.com Cc: beginners@haskell.org Message-ID: CAHRrG0rMHFLoo7L__VPr_CJL0QYhd3oy+VMvWDAffjLazC=g...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hi Aninda, Thanks for your reply. Unfortunately, I have already tried out these examples and they don't seem to work. HaskellNet has a github repo. I will contact the author and see whether I can find any solution. Thanks Salil On Tue, Sep 18, 2012 at 10:40 PM, Anindya Mozumdar anindya.lugb...@gmail.com wrote: Does anybody know of any good libraries I can use to send a mail via google's SMTP? I found SMTPClient and HaskellNet. The former does not support TLS and the latter does not seem to have examples for using TLS to send an email via SMTP. Did anybody manage to do that? A fellow beginner, so I don't have indepth knowledge of the subject. But can this help - http://stackoverflow.com/questions/8036680/haskell-smtp-over-ssl http://www.haskell.org/pipermail/beginners/2012-July/010190.html -- Message: 3 Date: Tue, 18 Sep 2012 17:41:52 +0100 From: Robert Wills wrwi...@gmail.com Subject: Re: [Haskell-beginners] Sending mail via SMTP To: Salil Wadnerkar rohsh...@gmail.com Cc: beginners@haskell.org Message-ID: CALVz20_wHYys0eR4eC-px9-zaXyF+0k9_rt36U7Fihk=ud5...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I do not believe there is and support for ssl in HaskellNet at present. It has I believe been looked at but it's not simple to implement. The best way of integrating tls would be to implement smtp over conduit as http-conduit does. On Tue, Sep 18, 2012 at 4:08 PM, Salil Wadnerkar rohsh...@gmail.com wrote: Hi Aninda, Thanks for your reply. Unfortunately, I have already tried out these examples and they don't seem to work. HaskellNet has a github repo. I will contact the author and see whether I can find any solution. Thanks Salil On Tue, Sep 18, 2012 at 10:40 PM, Anindya Mozumdar anindya.lugb...@gmail.com wrote: Does anybody know of any good libraries I can use to send a mail via google's SMTP? I found SMTPClient and HaskellNet. The former does not support TLS and the latter does not seem to have examples for using TLS to send an email via SMTP. Did anybody manage to do that? A fellow beginner, so I don't have indepth knowledge of the subject. But can this help - http://stackoverflow.com/questions/8036680/haskell-smtp-over-ssl http://www.haskell.org/pipermail/beginners/2012-July/010190.html ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 4 Date: Tue, 18 Sep 2012 10:01:14 -0700 From: Tim Perry tim.v...@gmail.com Subject: Re: [Haskell-beginners] Sending mail via SMTP To: beginners@haskell.org Message-ID: cafvgasxhhm6op0gqfiawmt0j4k9ynvztchnxvipjgqy0ksy...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Robert, are you saying you
Beginners Digest, Vol 51, Issue 28
Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than Re: Contents of Beginners digest... Today's Topics: 1. Re: FRP (Ertugrul S?ylemez) 2. Re: FRP (Darren Grant) 3. Re: FRP (Kim-Ee Yeoh) -- Message: 1 Date: Wed, 19 Sep 2012 04:35:18 +0200 From: Ertugrul S?ylemez e...@ertes.de Subject: Re: [Haskell-beginners] FRP To: beginners@haskell.org Message-ID: 20120919043518.543d2...@tritium.streitmacht.eu Content-Type: text/plain; charset=us-ascii Christopher Howard christopher.how...@frigidcode.com wrote: Which FRP framework (i.e., Haskell package) is the best one to play with for someone still trying to grasp the basics of FRP? In terms of tutorials and related blog posts I currently recommend reactive-banana. In terms of power and elegance I recommend Netwire. The main difference is that reactive-banana is both simple and easy. It implements classic FRP with the usual notion of behaviors and events. Heinrich strives to make it very accessible. Netwire follows a more algebraic path and drops the classic notion. The line between signals and events is blurred. It's a bit more difficult to understand, but is more expressive and concise. Also it's pretty much time-leak-free. The library is designed to be very elegant while preserving non-FRP performance to a high degree. (To be fair, I'm the author of Netwire.) =) Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. -- next part -- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: http://www.haskell.org/pipermail/beginners/attachments/20120919/df664793/attachment-0001.pgp -- Message: 2 Date: Tue, 18 Sep 2012 23:12:47 -0700 From: Darren Grant therealklu...@gmail.com Subject: Re: [Haskell-beginners] FRP To: Ertugrul S?ylemez e...@ertes.de Cc: beginners@haskell.org Message-ID: ca+jd6siwczslat-wcj6emvp4-2klncne5jib7heft+v7+6m...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 I don't know that netwire is more difficult to understand. I'm appreciating the network analogy and the generalisation of wires. Thanks for pointing it out! Cheers, Darren On Tue, Sep 18, 2012 at 7:35 PM, Ertugrul S?ylemez e...@ertes.de wrote: Christopher Howard christopher.how...@frigidcode.com wrote: Which FRP framework (i.e., Haskell package) is the best one to play with for someone still trying to grasp the basics of FRP? In terms of tutorials and related blog posts I currently recommend reactive-banana. In terms of power and elegance I recommend Netwire. The main difference is that reactive-banana is both simple and easy. It implements classic FRP with the usual notion of behaviors and events. Heinrich strives to make it very accessible. Netwire follows a more algebraic path and drops the classic notion. The line between signals and events is blurred. It's a bit more difficult to understand, but is more expressive and concise. Also it's pretty much time-leak-free. The library is designed to be very elegant while preserving non-FRP performance to a high degree. (To be fair, I'm the author of Netwire.) =) Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. ___ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners -- Message: 3 Date: Wed, 19 Sep 2012 13:35:32 +0700 From: Kim-Ee Yeoh k...@atamo.com Subject: Re: [Haskell-beginners] FRP To: Christopher Howard christopher.how...@frigidcode.com Cc: Haskell Beginners beginners@haskell.org Message-ID: CAPY+ZdT55PX8=o3ja-z5nykjl_jqj-btlrpabtddjczq9gf...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 On Wed, Sep 19, 2012 at 4:20 AM, Christopher Howard wrote: Which FRP framework (i.e., Haskell package) is the best one to play with for someone still trying to grasp the basics of FRP? I think of FRP as a Dream that's still being worked on. So to get at the basics of the Dream I do a lot of gedankenexperiment, sketching on pen and paper, and code fragments. I read Conal Elliott's blog to gather the results of his investigations of that Dream. But I understand that you're a practical kind of guy and prefers to push and poke to learn stuff, and I think
