Re: [Haskell-cafe] Haskell Platform and Leksah on Windows
Hi, If you go the EclipseFP approach, you may have installations troubles too. In my case, it was due to having a version of GHC and libraries that EclipseFP doesn't like. Once I got it to work, I loved it. David. 2013/8/8 Dorin Lazar : > Hi, > I understood what's wrong about my approach - and since I want to use > an IDE to assist me, I will try both EclipseFP and Sublime Text, to > see how that works. My feeling was that since the leksah website > suggested that cabal is the way to do it and since when I search for a > Haskell IDE that is it, then it was obvious that the recommended way > doesn't work as it should. In my mind the platform was broken, I > understand now that it's not the platform, just this special way of > using it. > > I was also in awe of the fact that nobody really says anything about > these difficulties, and felt like an estranged child that messed > things up badly; however, it seems that the real issue is that nobody > really does it that way, and I was wrong to actually try it like that. > As I said (or haven't, but will) once I will get the hang of it I will > recount my experience for others to follow, hopefully in better terms > than this frustrating first experience. > > Many thanks for everyone's advice on the list, > Dorin > > On Thu, Aug 8, 2013 at 9:48 PM, Carter Schonwald > wrote: >> Hey Dorin, >> I don't understand your claims. >> >> 1) haskell has worked perfectly well on windows for quite some time. I used >> HUGs nearly a decade ago, and in more recent time (2-3 years ago) I helped >> teach an introductory first computer science class using GHC where many >> students were doing great work using notepad++ and ghci. >> >> I don't understand your focus on emacs and make files. >> >> 2) if you want an "IDE" experience, Sublime Text with the right plugins, or >> perhaps EclipseFP are worth checking out. >> >> 3) likewise, if you're finding tooling on windows unsatisfactory, help fix >> it! Bug reports, patches, or new tools and libraries are always welcome. >> Haskell is a relatively small community, and thusly limited manpower (we're >> all volunteers), so way to fix any problem is help out! >> >> cheers >> >> >> On Thu, Aug 8, 2013 at 3:30 AM, Dorin Lazar wrote: >>> >>> Hello, >>> I am the original author of the post, and I finally received the >>> emails from the mailman (probably there was an issue with the >>> automated requests). >>> My answers are inlined. >>> >>> > 1) Leksah should not be considered an "official haskell ide", but merely >>> > one of >>> > many community supported editing tools. And frankly one of the less >>> > widely >>> > used ones at that! Leksah is not used much at all by anyone, though >>> > theres >>> > probably a handful of folks who do use it. >>> > Many folks use editors like Sublime Tex (2/3), Emacs, Vi(m), textmate, >>> > and >>> > many more. Its worth noting that the sublime-haskell plugin for sublime >>> > text, and analogous packages for many other editors, provide haskell >>> > IDE-like powers, or at least a nice subset thereof. >>> Unfortunately, I think the problem with this is that we have a >>> different vision on how development should be done. I have extensive >>> experience of working from console, with a simple text editor and >>> hand-made Makefiles or anything similar. However, an IDE should be a >>> productivity tool, that can help you improve your understanding of the >>> language, and can assist you in following the proper syntax for a new >>> language. While learning by doing 'write, save, compile, examine error >>> message' is ok with me, it is slow, and it limits the time I can >>> dedicate to learning the language itself. A better cycle is the >>> current 'write, examine error message' of most IDEs, since it's faster >>> and requires no context switch. Sure, editors can help there. IDEs do >>> this by default. >>> So it's normal of me to search for an IDE to better learn the >>> language, I'll leave the emacs + console version for when I am >>> productive in the language. >>> >>> > 2) There are people working on building better easily portable native >>> > gui >>> > toolkits, but in many respects, a nice haskelly gui toolkit is still >>> > something people are experimetning with how to do well. theres lots of >>> > great >>> > tools out as of the past year or two, many more in progress on various >>> > time >>> > scales, and gtk2hs is great for linux (and thats fine). >>> Unfortunately, this is not what's advertised. In fact, on the leksah >>> site, the recommended method is to have the IDE installed via cabal. >>> In another mail Mihai calls me unreasonable, but I think it's >>> reasonable to think that the recommended method should be the one that >>> works. >>> But the easy to tell truth is that the Haskell Platform for Windows >>> is not mature enough yet. That is something I can understand, and I >>> can recommend other beginners to install a Linux VM for Haskell. That >>> is perfectly
Re: [Haskell-cafe] Hackage Update Brigade
2013/5/28 Conrad Parker : > For that proposal, there is also an informal github group for updating > unmaintained packages, > which anyone willing is welcome to join: Say I would be willing to spend a few hours a month to fix some problems, but I'm not very experienced; I only use haskell for a few small programs at work, I'm not used to working collaboratively (but willing to learn) Would I still be able to be useful ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for portable Haskell or Haskell like language
I've got ghc working here on a centos 5.5 machine. But without root privilege, I don't know how. Perhaps you can use a virtual machine with centos 5.5 (you'd have root access on this machine), install ghc on this machine, compile your programs there, then transfer that on the first computer ? 2013/4/27 Christopher Howard > Hi. I've got this work situation where I've got to do all my work on > /ancient/ RHEL5 systems, with funky software configurations, and no root > privileges. I wanted to install GHC in my local account, but the gnu > libc version is so old (2.5!) that I can't even get the binary packages > to install. > > I've had success installing some other simple functional languages (like > CLISP) on these same systems, so I was wondering if there was perhaps > another language very similar to Haskell (but presumably simpler) with a > super portable compiler easily built from source, which I could try. > > I'll admit -- I haven't tried the HUGS compiler for Haskell. The quick > description didn't make it sound much more portable than GHC, but I > guess I could try it if I heard some good reasons to think it would be > more portable. > > -- > frigidcode.com > > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Prolog-style patterns
Hi Jan, On one hand, I've never really needed this. On the other hand, it looks like a nice syntaxic sugar addition, so if you implemented this I would probably give it a try. David. 2013/4/8 Jan Stolarek > > You can achieve something similar with the ViewPatterns language > > extension. > > > > member _ [] = False > > member x (((x ==) -> True) : _) = True > > member x (_ : xs) = member x xs > Hi Tillmann, > > there are a couple of ways to achieve this in Haskell, for example using > guards: > > member :: Eq a => a -> [a] -> Bool > member _ [] = False > member y (x:_) | x == y = True > member y (_:xs) = member y xs > > The goal of my proposal is to provide a concise syntax, whereas > ViewPatterns are very verbose and > guards are slightly verbose. I want something simple and something that is > very intuitive if > you've programmed in Prolog :) > > Janek > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] introducing Maybe at managing level
The link to LYAH that John provided, http://learnyouahaskell.com/making-our-own-types-and-typeclasses , doesn't mention monad at all. Laziness is mentionned only once while explaining recursive types, but you could omit that line. Now Algebraic is mentionned 6 times, but if you're afraid it might scare someone, why not replace it by 'Haskell' ( thus, Algebraic data type becomes Haskell data type, for the purpose of your introduction ) 2013/3/29 Luc TAESCH : > Thanks John. > > I was indeed thinking to Maybe and the monad bindings, > and LYAH, or http://book.realworldhaskell.org/read/error-handling.html > > the problems is I cannot uses these links in isolation ( to a Non > haskellers) because they mention Monads, Lazyness, Algebric types, all this > vocabularies that side track a beginner, ( or a manager ;-) > > then all I want to show is the generic concept ( powerpoint level) > of how a forest of (non core) case can be streamlined in one major case ( > the good outcome) , and all the rest ( exceptions in a non technical sense) > are catched by the maybe monad, without sidetracking the readability of the > code . > > I saw this somewhere on the blogosphere, but cannot remember where.. > > this is management level, and this is even worse than beginners techies, > because they derails very quickly when talking "details" > > > -- > Luc > be.linkedin.com/in/luctaesch/ > Envoyé avec Sparrow > > Le vendredi 29 mars 2013 à 06:47, John Lato a écrit : > > In FP, I think this sort of problem is generally handled via algebraic data > types rather than exceptions. In particular this directly addresses the > issue of "exceptions don't necessarily shout themselves out", since the > compiler warns you if you've missed a case. > > They sound mathy, but algebraic data types are actually a pretty simple > concept. I think the "Learn You a Haskell" explanation is decent: > http://learnyouahaskell.com/making-our-own-types-and-typeclasses > > Provided I understand the context properly, actually using exceptions for > this sort of issue would be extremely rare practice. > > > On Fri, Mar 29, 2013 at 12:21 AM, luc taesch wrote: > > I was looking for some link introducing the way FP/ Haskell handles errors > and Exceptions. > > This is for a non FP Guy, and ideally withought scaring them with Monads and > category theory :-). > > for the background : > > the guy said : As I mentioned in another thread in banking (in particular) > it is the exception processing that often dominates the functionality of a > system - as the core concept is generally very straightforward. Developing > for "exception handling" (not in a Java/C++ sense) is a tricky thing - as > the exception don't necessarily shout themselves out - and are often why we > have large misunderstood legacy systems which are hard to replace. > > > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Non polymorphic numerals option -- avoiding type classes
Prelude> :t [[1,2],3] you have a list with 2 elements: - [1,2] - 3 the type of [1,2] is [Integer] the type of 3 is Integer But all elements in a list must have the same type. 2012/12/27 Rustom Mody : > > > On Thu, Dec 27, 2012 at 1:48 AM, Roman Cheplyaka wrote: >> >> * Rustom Mody [2012-12-26 20:12:17+0530] >> > So is there any set of flags to make haskell literals less polymorphic? >> >> Yes, there is! >> >> % ghci -XRebindableSyntax >> GHCi, version 7.6.1: http://www.haskell.org/ghc/ :? for help >> Loading package ghc-prim ... linking ... done. >> Loading package integer-gmp ... linking ... done. >> Loading package base ... linking ... done. >> > import Prelude hiding (fromInteger) >> Prelude> let fromInteger = id >> Prelude> :t 3 >> 3 :: Integer >> >> Roman > > > > Thanks Roman -- that helps. > And yet the ghci error is much more obscure than the gofer error: > > --- contents of .ghci --- > :set -XRebindableSyntax > let fromInteger = id > -- ghci session - > $ ghci > GHCi, version 7.4.1: http://www.haskell.org/ghc/ :? for help > > Loading package ghc-prim ... linking ... done. > Loading package integer-gmp ... linking ... done. > Loading package base ... linking ... done. > Prelude> :t 5 > 5 :: Integer > Prelude> :t [[1,2],3] > > :1:8: > Couldn't match expected type `[Integer]' with actual type `Integer' > Expected type: Integer -> [Integer] > Actual type: Integer -> Integer > In the expression: 3 > In the expression: [[1, 2], 3] > > > - The same in gofer - > Gofer session for: > pustd.pre > ? :t [[1,2],3] > > > ERROR: Type error in list > *** expression : [[1,2],3] > > *** term : 3 > *** type : Int > *** does not match : [Int] > -- > So the error is occurring at the point of the fromInteger (= id) but the > message does not indicate that > > -- > http://www.the-magus.in > http://blog.languager.org > > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Survey: What are the more common Haskell IDEs in use ?
I often use geany too 2012/11/24 Erik de Castro Lopo : > Dan wrote: > >> Because I see there are many preferences on what IDE to use for Haskell >> I've created a quick survey on this topic. >> >> Please click here and select your choices from the lists. >> >> http://kwiksurveys.com/s.asp?sid=oqr42h4jc8h0nbc53652 >> >> >> Any comments/suggestions are welcome. > > I use Geany which is not on the list. > > Erik > -- > -- > Erik de Castro Lopo > http://www.mega-nerd.com/ > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell showcase in 5 minutes
Le 28 février 2012 14:45, Doug McIlroy a écrit : > Here's an example that fits comfortably in 5 minutes--if > your audience knows elementary calculus: > http://www.cs.dartmouth.edu/~doug/powswer.html 404 invalid url ! David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Cafe Tag (was: Optimizations and parallel execution in the IO for a small spellchecker)
Le 15 février 2012 21:32, JP Moresmau a écrit : > OK, thanks all, I can stop worrying being an uncouth Frenchman, then... Not that I post a lot, but you had me worried for a while, too. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Poll: Do you want a mascot? -- please stop this
2011/11/23 Giovanni Tirloni : > 2. It floods people with email they don't care (unless they care to keep > track of the results) Not that I care that much about a mascot (I like the lamb though), but a few threads about it hardly counts for a flooding. Besides, a good email client would allows to group emails that belong together (a thread) and mute them. Also, this is café, right ? Aren't people subscribed to this list supposed to expect a broad range of topics ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data.Text.IO.hGetContents problem on windows
Re-bonjour Café, Bryan, > I have a program that works fine on linux, but doesn't on windows. > Is there something I'm doing wrong ? Checking the source code for Data.Text.IO.hGetContents, I see that the only time hFileSize is used is in chooseGoodBuffering when the buffering is in block mode, so I have a workaround: I just set the buffering in line mode, which forks for my case. The documentation for hFileSize says "For a handle hdl which attached to a physical file, hFileSize hdl returns the size of that file in 8-bit bytes." So chooseGoodBuffering should check if the handle is a physical file before trying to optimize the buffer size, right ? However, I'm not sure how to check if the handle is a physical file. hIsTerminalDevice wouldn't help here, I guess. hIsSeekable give this on windows : : hIsSeekable: invalid argument (Bad file descriptor) Maybe the solution would be to try hFileSize, and set a default buffering if an exception is caught ? David. > > David. > > The source code of the part that fails is as follows: > > -- Execute a command on a distant server using the rexec protocol. > rexec :: HostName -- server to connect to > -> Text -- user > -> Text -- password > -> TextEncoding -- server's text encoding > -> Text -- command to execute > -> IO (Maybe Text) > rexec !ip !ru !rp !enc cmd = handle rexec_error $ do > hdl <- connectTo ip (PortNumber 512) > let end_param = T.singleton (chr 0) > ctrl_string = T.concat [ > "0", end_param, > ru, end_param, > rp, end_param, > cmd, end_param > ] > hSetEncoding hdl enc > TIO.hPutStr hdl ctrl_string > -- make sure the control string is sent. > hFlush hdl > -- 1st char read is actually a error code which we ignore for now > hGetChar hdl > !res <- TIO.hGetContents hdl > hClose hdl > return (Just res) > > rexec_error :: SomeException -> IO (Maybe Text) > rexec_error err = do > putStrLn $ show err > return Nothing > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Data.Text.IO.hGetContents problem on windows
Bonjour Café, bonjour Bryan I have a program that works fine on linux, but doesn't on windows. On windows XP with the latest Haskell platform, I get: : hFileSize: invalid argument (Bad file descriptor) I think the problem is with hGetContents from Data.Text.IO, but my google-fu failed to help me find any information. Is there something I'm doing wrong ? David. The source code of the part that fails is as follows: -- Execute a command on a distant server using the rexec protocol. rexec :: HostName -- server to connect to -> Text -- user -> Text -- password -> TextEncoding -- server's text encoding -> Text -- command to execute -> IO (Maybe Text) rexec !ip !ru !rp !enc cmd = handle rexec_error $ do hdl <- connectTo ip (PortNumber 512) let end_param = T.singleton (chr 0) ctrl_string = T.concat [ "0", end_param, ru, end_param, rp, end_param, cmd, end_param ] hSetEncoding hdl enc TIO.hPutStr hdl ctrl_string -- make sure the control string is sent. hFlush hdl -- 1st char read is actually a error code which we ignore for now hGetChar hdl !res <- TIO.hGetContents hdl hClose hdl return (Just res) rexec_error :: SomeException -> IO (Maybe Text) rexec_error err = do putStrLn $ show err return Nothing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: EclipseFP 2.1.0 released
Is it possible to install it with GHC7.2 ? I tried and it can't compile scion. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCI Feature Request: Last Successful Compilation State Saved
2011/8/27 aditya siram : > Hi all, > I would like for the GHCI interpreter to save its environment before > reloading a file and allowed the user to revert back to that state if the > compilation was unsuccessful. That would be awesome. I would like this too. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Call for GUI examples - Functional Reactive Programming
2011/7/8 Heinrich Apfelmus : > I want to hear! > Just a description. :) You can also mention why you find it interesting etc. Well I have an old program sitting around. Anyway, it's very simple : The GUI has - a window with a menu bar, 2 directory selects (source and dest directories), 1 file select ( the 'patch file'), 1 textview to write logging information, and a 'Convert' button to start. - an about window that opens from a 'About...' menuitem - A status bar. The convert button stats an action that scans all applicable files in a source directory, converts them and writes them in a destination directory. The conversion itself is irrelevant to the topic, in my case it consists in searching for patterns in the file and replacing them, according to a list of changes read from a file, the 'patch file'. The progression is logged in the textview: file processed, strings replaced. In the status bar, a percentage bar grows. Why do I find it interesting ? Most of the time I would do a program like the above with a command line interface only. GUI programming can be tedious. Would FRP offer a way to code such a simple, boring example in a fun way ? Also, FRP is often concerned with animations, but I'd really like to see if it works well for small utilities. I have an old source code I can share, using gtk2hs, imperative style (and also beginner-ugly style :) ). It's about 200 lines of codes and a glade file. It just compiled and ran fine here. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Call for GUI examples - Functional Reactive Programming
2011/7/8 Heinrich Apfelmus : > Do you know any *small GUI programs* that you would *like* to see > *implemented with Functional Reactive Programming?* I may have an example. > I would love to hear your examples, so that I can try to convert them to FRP > style and test my library against them! You want a description of the example, or the complete source code to make it work ? Cheers, David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] mysql-simple - your go-to package for talking to MySQL
> You can access the docs on a slightly earlier version:
> http://hackage.haskell.org/package/mysql-simple-0.2.2.0
That's what I did.
> The doc specifies it here:
>> convertError :: [Field] -> [Maybe ByteString] -> Int -> a
>> Throw a ConversionFailed exception, indicating a mismatch between the number
>> of columns in the Field and row, and the number in the collection to be
>> converted to.
> So if you're making an instance for a type that takes ten items from
> the collection, then put 10. Could always make this clearer.
That wasn't clear to me, but English isn't my first language, so maybe
that's why.
>> To try, I put 0, and the test compiled. However, I had a connection
>> error number 1312, saying my procedure "can't return a result set in
>> the given context". (The query I used works from the mysql
>> command-line interface)
> Ah, I wouldn't know about that, I haven't used the mysql version.
I tried again with that code:
data PlateauSel = PS
{ psPlat :: Int
, psArm :: Maybe Int
, psTaille :: Int
, psType :: Int
, psEtat :: Int
, psLoc :: Int
, psDest :: Int
, psCol :: Int
, psEtg :: Int
, psNiv :: Int
, psPos :: Int
, psRes :: Int
}
instance QueryResults PlateauSel where
convertResults [fa,fb,fc,fd,fe,ff,fg,fh,fi,fj,fk,fl]
[va,vb,vc,vd,ve,vf,vg,vh,vi,vj,vk,vl]
= PS a b c d e f g h i j k l
where !a = convert fa va
!b = convert fb vb
!c = convert fc vc
!d = convert fd vd
!e = convert fe ve
!f = convert ff vf
!g = convert fg vg
!h = convert fh vh
!i = convert fi vi
!j = convert fj vj
!k = convert fk vk
!l = convert fl vl
convertResults fs vs = convertError fs vs 12
hello :: IO [PlateauSel]
hello = do
conn <- connect myConnectInfo
query_ conn "call Plateau_Select(1)"
But there's no improvement :
*Main> hello
*** Exception: ConnectionError {errFunction = "query", errNumber =
1312, errMessage = "PROCEDURE robot.Plateau_Select can't return a
result set in the given context"}
*Main>
The problem isn't with the stored procedure, it works if I call it
from the mysql client.
(@x.x.x.x) [robot] (;)> call Plateau_Select(1);
+---+---++--+--+--+-+-+---++--+-+
| IdPlateau | IdArmoire | Taille | Type | Etat | Localisation |
Destination | Colonne | Etage | Niveau | Position | Reserve |
+---+---++--+--+--+-+-+---++--+-+
| 1 | NULL | 1 |2 |1 |1 |
1 | 0 | 0 | 0 |0 | 1 |
+---+---++--+--+--+-+-+---++--+-+
1 row in set (0.03 sec)
Another information: it doesn't work either with HDBC-mysql, but it
does work with HDBC-odbc.
Another unrelated thing : the documentation states that the Query type
is designed to make it difficult to create queries by concatenating
strings.
I found out there are situations where you don't have a choice.
For example, how to write a function that returns the columns of a
table using show columns ?
type Champ = (String,String,String,String,String,String)
getColumns :: Connection -> String -> IO [Champ]
getColumns conn table = do
query_ conn (fromString $ "show columns from " ++ table)
if you try query conn "show columns from " ( Only table), the query built is
show columns from 'x'
which fails.
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Re: [Haskell-cafe] [ANN] mysql-simple - your go-to package for talking to MySQL
2011/5/2 Bryan O'Sullivan :
> Hi, folks -
> Over the past few days, I've released two MySQL-related packages on Hackage
> that I think should be pretty useful.
> The first is mysql-simple: http://hackage.haskell.org/package/mysql-simple
> This is a mid-level binding to the MySQL client API. I aimed it squarely at
> being both fast and easy to use, and I'm very pleased with the results so
> far.
Hello,
Some feedback about a very first try with your library;
First of all, thanks a lot for releasing it, I hope it'll make many
people's life easier.
Also, thanks for taking the time to write a nice, thorough documentation.
The library was easy to install, thanks to cabal -- no troubles here.
I had trouble accessing the documentation : the last versions on
hackage have a build failure, so the doc isn't available. I was able
to see the documentation for mysql-simple-0.2.2.0 though.
The very first example didn't work for me :
{-# LANGUAGE OverloadedStrings #-}
import Database.MySQL.Simple
hello = do
conn <- connect defaultConnectInfo
query conn "select 2 + 2"
Couldn't match expected type `IO b'
against inferred type `q -> IO [r]'
In the expression: query conn "select 2 + 2"
In the expression:
do { conn <- connect defaultConnectInfo;
query conn "select 2 + 2" }
In the definition of `hello':
hello = do { conn <- connect defaultConnectInfo;
query conn "select 2 + 2" }
Using query_ instead of query brings a new error:
Ambiguous type variable `r' in the constraint:
`Database.MySQL.Simple.QueryResults.QueryResults r'
arising from a use of `query_' at ftmsql.hs:7:3-28
Possible cause: the monomorphism restriction applied to the following:
hello :: IO [r] (bound at ftmsql.hs:5:1)
Probable fix: give these definition(s) an explicit type signature
or use -XNoMonomorphismRestriction
Easily corrected, adding the pragma.
Next step was to try it, which took me a few steps:
*Main> hello
:1:0:
Ambiguous type variable `r' in the constraint:
`Database.MySQL.Simple.QueryResults.QueryResults r'
arising from a use of `hello' at :1:0-4
Probable fix: add a type signature that fixes these type variable(s)
*Main> hello :: IO [Only Int]
*** Exception: Incompatible {errSQLType = "LongLong", errHaskellType =
"Int", errMessage = "types incompatible"}
*Main> hello :: IO [Only Int64]
:1:18: Not in scope: type constructor or class `Int64'
etc.
I would like to suggest modifying the exemple in the documentation to
look like this
--
{-# LANGUAGE OverloadedStrings #-}
import Database.MySQL.Simple
import Data.Int
myConnectInfo = defaultConnectInfo { connectHost = "x.x.x.x",
connectUser= "xx", connectPassword="", connectDatabase="xxx" }
hello :: IO [Only Int64]
hello = do
conn <- connect myConnectInfo
query_ conn "select 2 + 2"
--
That way a beginner has a starting point that compiles and that he can
run as is.
Next I modified the simple example to call a stored procedure, it
returns a resultset of 12 columns.
Unfortunately, I realised that QueryResults instances are defined up
to 10 elements only.
However, the documentation shows how to define a QueryResults
instance, so I created a datatype and tried to define the instance,
and got stuck with an error:
Couldn't match expected type `PlateauSel'
against inferred type `Int -> a'
In the expression: convertError fs vs
In the definition of `convertResults':
convertResults fs vs = convertError fs vs
In the instance declaration for `QueryResults PlateauSel'
Indeed, the documentation shows that convertError takes 3 parameters,
and I gave, as per the example, only 2.
But I'm not sure what to write for the 3rd parameter, the
documentation doesn't help me here.
To try, I put 0, and the test compiled. However, I had a connection
error number 1312, saying my procedure "can't return a result set in
the given context". (The query I used works from the mysql
command-line interface)
I'm not sure if that means Database.MySQL supports calling stored
procedures that return a result set or not. I suspect not. Perhaps it
would be useful to add it in the documentation.
Thanks,
David.
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Re: [Haskell-cafe] How unique is Unique
2011/5/27 Emil Axelsson : > Does anyone have any comments on the proposed solution? Are there any > alternatives available? It might be unsuitable where an administrator can change the system's time while the program is running. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parallel compilation and execution?
2011/5/26 michael rice
> Thank, Daniel
>
> Multiple threads are in evidence in my system monitor, but I wonder why I'm
> getting two different answers, one twice the other. The first is the
> parallel solution and the second is the non.
>
Why do you add n1+n2+1 in the parallel program, but only n1+n2 in the
non-parallel one ?
>
> Michael
>
> ===
>
> {-
> import Control.Parallel
>
> nfib :: Int -> Int
> nfib n | n <= 1 = 1
>| otherwise = par n1 (pseq n2 (n1 + n2 + 1))
> where n1 = nfib (n-1)
>n2 = nfib (n-2)
> -}
>
> nfib :: Int -> Int
> nfib n | n <= 1 = 1
>| otherwise = nfib (n-1) + nfib (n-2)
>
> main = do putStrLn $ show $ nfib 39
>
> =
>
> [michael@hostname ~]$ ghc --make -threaded nfib.hs
> [1 of 1] Compiling Main ( nfib.hs, nfib.o )
> Linking nfib ...
> [michael@hostname ~]$ ./nfib +RTS -N3
> 204668309
> [michael@hostname ~]$ ghc --make nfib.hs
> [1 of 1] Compiling Main ( nfib.hs, nfib.o )
> Linking nfib ...
> [michael@hostname ~]$ ./nfib
> 102334155
> [michael@hostname ~]$
>
>
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Re: [Haskell-cafe] ANNOUNCE: iterIO-0.1 - iteratee-based IO with pipe operators
2011/5/6 Ertugrul Soeylemez : > David Mazieres wrote: >> Please enjoy. I'd love to hear feedback. > Thanks a lot, David. This looks like really good work. I'm using the > 'enumerator' package, and looking at the types your library seems to use > a similar, but more complicated representation. Is there any particular > reason, why you didn't base your library on an existing iteratee package > like 'enumerator'? David has documented some design decisions in http://hackage.haskell.org/packages/archive/iterIO/0.1/doc/html/Data-IterIO.html#g:3 Perhaps you may find some answers there. David (another one :) ) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: iterIO-0.1 - iteratee-based IO with pipe operators
2011/5/6 David Mazieres : > * Every aspect of the library is thoroughly document in haddock > including numerous examples of use. I'm reading the documentation, it's impressively well detailed. It has explanations, examples, all that one could dream for. Thanks ! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Programming Chalenges: The 3n+1 problem
2011/4/14 Sebastian Fischer > > The advantage of this complicated definition is that you get a > memoized version of the `fibonacci` function simply by using `fixmemo` > instead of `fix`: > Wow. I think something about 'fix' just made sense thanks to your post, though I had read a few blog posts about it. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell mail server fail?
2011/3/10 wren ng thornton > Like Kenneth Hoste, I haven't been receiving mails from haskell-cafe@ nor > libraries@ for a few days to a week now. What is the status of the mailing > lists? > I don't have the status, but I am still receiving emails from cafe and libraries. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell IDE
2011/3/7 David Virebayre > And build success. Now to open a haskell source file and play with > Eclipse. > ... and I keep having those "Problem occurred" popups: 'Occurrences has encountered a problem An internal error has occurred. In the detail: An internal error has occurred. java.lang.NullPointerException In show error log tab, 3 messages; all have 'net.sf.eclipsefp.haskell.ui' in the Plug-in column : TWICE: eclipse.buildId=M20100211-1343 java.version=1.6.0_20 java.vendor=Sun Microsystems Inc. BootLoader constants: OS=linux, ARCH=x86, WS=gtk, NL=fr_FR Framework arguments: -product org.eclipse.sdk.ide Command-line arguments: -product org.eclipse.sdk.ide -data /data/code/eclipse/../runtime-New_configuration -dev file:/data/code/eclipse/.metadata/.plugins/org.eclipse.pde.core/New_configuration/dev.properties -os linux -ws gtk -arch x86 Info Mon Mar 07 15:15:13 CET 2011 cabal executable: /usr/local/bin/cabal, cabal-install 0.8.2, Cabal library version 1.8.0.2 AND ONCE: eclipse.buildId=M20100211-1343 java.version=1.6.0_20 java.vendor=Sun Microsystems Inc. BootLoader constants: OS=linux, ARCH=x86, WS=gtk, NL=fr_FR Framework arguments: -product org.eclipse.sdk.ide Command-line arguments: -product org.eclipse.sdk.ide -data /data/code/eclipse/../runtime-New_configuration -dev file:/data/code/eclipse/.metadata/.plugins/org.eclipse.pde.core/New_configuration/dev.properties -os linux -ws gtk -arch x86 Info Mon Mar 07 15:03:33 CET 2011 cabal executable: /home/david/bin/cabalinit, cabal-install , Cabal library version Cheers, David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell IDE
2011/3/3 JP Moresmau : > Hello, I'm one of the maintainers of EclipseFP. It is a real > alternative: it works, it is maintained, supported and enhanced. I use > it for my own projects, and of course I use it to work on the version > of the scion library that ships with it, so we eat our own dogfood > :-). A new minor version is going to come out in the next couple of > weeks. Why don't you give it a try? We appreciate any feedback! from http://eclipsefp.sourceforge.net/eclipsefp2.html I understand that building scion is automatically done, but can be optionally done it it's too long. but from http://eclipsefp.sourceforge.net/build.html I see that I do have to build it. But : git clone http://github.com/JPMoresmau/scion.git Initialized empty Git repository in /data/code/scion/.git/ remote: Counting objects: 3563, done. remote: Compressing objects: 100% (1310/1310), done. remote: Total 3563 (delta 2137), reused 3342 (delta 1970) Receiving objects: 100% (3563/3563), 580.09 KiB | 395 KiB/s, done. Resolving deltas: 100% (2137/2137), done. david@pcdavid:~/code$ cd scion/ david@pcdavid:~/code/scion$ sudo cabal install [sudo] password for david: Resolving dependencies... cabal: dependencies conflict: ghc-6.12.3 requires Cabal ==1.8.0.6 however Cabal-1.8.0.6 was excluded because scion-0.1.0.8 requires Cabal ==1.6.* I'm not sure what to do now. Trying to install eclipsefp without scion built in case it works, but I'm not used to eclipse, I could use some screenshots to take me step by step through the process. For example, My "project" menu has open grayed, and file/import wants me to choose an import source (I chose Existing project into workspace) but then do I copy projects into workspace ( I did not ) I have eclipse already setup with android development (I have just a toy project, I planned to learn about android programming), when I imported the projects they appeared at the same place. Is there a way not to mix android and haskell projects ? Do I create a new workspace, or assign working sets ? Anyway the projects are in the workspace, and there's 123 warnings; but I can't really tell if the build failed or not. Selecting all the project, and right-click - refresh didn't seem to change anything. But it seems it worked, because step 7 does launch a new eclipse window, and I can see haskell in the preferences. Except that I had an error message regarding scion, and stupid me, clicked ok before I could remember what was written. I tried rebuild scion, but nothing seemed to happen. I closed the first Eclipse window (the one that has all the eclipsefp projects in the package explorer), but then the second one closed too. I lauched eclipse again, run configurations, etc and this time it looks like scion is building (well something happens in the Console tab) While this is building, I'm wondering if there's a way to launch eclise directly in the right "mode". Not having to go to run configurations, etc. Ah, the build failed. Complains that HUnit is missing. So I cabal install it, close my Eclipse window, run configurations again on the first Eclipse window, and the build resumes. And build success. Now to open a haskell source file and play with Eclipse. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell IDE
I use kate too. I tried and liked leksah, but the fact that everything is a project with a cabal file felt to heavy for me when I just want to hack on a single .hs file. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rendering of in new wiki (MSIE6)
> Statistics from "A tour of the Haskell Monad functions" (on my site), after > 15.351 pageviews: I find it surprising that nobody using google chrome ever browsed your site. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] the beginning of the end
2010/12/5 Andrew Coppin > I get Haskell. It's a programming language. You write programs with it. I get > VB - even if I think it sucks. But something like Stack Overflow, I find > myself just staring at it thinking "what the hell /is/ this thing?" It's quite simple. Level 1 - You have an unresolved programming problem. You ask the question on stack overflow. People give you answers. - You can (if you wish) provide answers for questions others have asked. Level 2 To weed out bad material, answers and questions are voted up or down (supposedly) based on their pertinence, by the users. Level 3 Each upvote earns a user some points, and the opposite for a downvote. Users then have a score. Answers from a user with a high score might be more reliable. Level 4 There is a system of badges to earn, perhaps so that one finds some extra amusement in helping others. Level 5 I'm out of layers here. I think this is all there is to it. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Question about TagSoup
Hello café,
I have seen tutorials about extracting information from a tag soup, but I
have a different use case:
I want to read a xml file, find a tag, change its content, and write the xml
file back.
This is an example of the files
http://ns.adobe.com/AdobeInDesign/idml/1.0/packaging"; DOMVersion="7.0">
zzznba5
Assuming I want to change the content of the "Content" tag, this is what I
came up with (simplified), I'm using direct recursion. Is there a better way
?
ts = do
soup <- parseTags `fmap` readFile "idml/h00/Stories/Story_ub9fad.xml"
writeFile "test" $ renderTagsOptions renderOptions{optMinimize = const
True}
$ modif soup
modif [] = []
modif (x@(TagOpen "Content" []):TagText _m : xs) = x : TagText "modified" :
modif xs
modif (x:xs) = x : modif xs
David.
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Re: [Haskell-cafe] GHC 7.0.1 developer challenges
2010/11/30 Ryan Ingram > On Mon, Nov 29, 2010 at 12:36 AM, Simon Peyton-Jones > wrote: > > Do you have an alternative to suggest? After all, the previous situation > wasn't good either. > > I suggest that we should be able to specify RTS options at > compile/link time, or as pragmas in the Main module. > That would be nice. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Catching up on Time and Directory
2010/11/16 Jon Fairbairn : > I'm probably terribly out of date with this, so I wonder if > anyone can save me the bother of working out what the > /preferred/ libraries are for (a) determining the > last-modified-time of a file or directory and (b) manipulating > the resulting time datum. > > I can find System.Directory.getModificationTime and > Data.Time.formatTime, but using them together seems unduly > awkward. I'm interested too. There's so many times and dates types it's confusing. I had a problem last week, got it to compile but I'm not sure I'm doint it right. ( asked but got no replies on the list ) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Is there a better way to convert from UTCTime to EpochTime ?
I want to set a file's modification time to the time I got from exif data. To get the time from exif, I found : Graphics.Exif.getTag :: Exif -> String -> IO (Maybe String) To set the file modification time, I found : System.Posix.Files.setFileTimes :: FilePath -> EpochTime -> EpochTime -> IO () Assuming I do find a Time in Exif, I need to convert a String to an EpochTime. - With parseTime I can get a UTCTime. - With utcTimeToPOSIXSeconds I can get a POSIXTime - With a POSIXTime I can more or less get an EpochTime To convert from a UTCTime to EpochTime this typechecks, but I'm not sure it's correct : fromIntegral . fromEnum . utcTimeToPOSIXSeconds $ etime This is part of a function getTime that will return the time from Exif data, if present, otherwise the file's modification time : getTime (path,stat) = do let ftime = modificationTime $ stat err (SomeException _) = return ftime time <- liftIO $ handle err $ do exif <- Exif.fromFile path let getExifTime = MaybeT . liftIO . Exif.getTag exif res <- runMaybeT $ do tmp <- msum . map getExifTime $ [ "DateTimeOriginal", "DateTimeDigitized", "DateTime" ] MaybeT . return . parseTime defaultTimeLocale "%Y:%m:%d %H:%M:%S" $ tmp case res of Nothing-> return ftime Just etime -> return . fromIntegral . fromEnum . utcTimeToPOSIXSeconds $ etime return (path,time) Questions : 1) is there a better way to convert the time ? 2) any general comments on getTime ? Thanks, David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] "Haskell is a scripting language inspired by Python."
<< Also they "don't scale well", which I guess means that they don't make it inconvenient to design badly. >> Luke Palmer I nominate the above for quote of the week ! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] In what language...?
2010/10/25 Gregory Collins > Andrew Coppin writes: > > Hypothesis: The fact that the average Haskeller thinks that this kind of > > dense > > cryptic material is "pretty garden-variety" notation possibly explains why > > normal people think Haskell is scary. > That's ridiculous. That's not so ridiculous in the sense that some people might (wrongly) think they won't understand haskell until they understand at least some of that cryptic material. Many long discussion about Haskell on reddit seem to have a beginner thinking he must "understand monads" before going on. Yes, the famous monads which aren't that complicated at all, still they are part of this dense cryptic material when you're a newbie that used to think he's smart because he knows c, pascal, basic, php , and learned postscript's basics in a few days (Then you start looking at this curiosity called haskell, and you stumple upon haskell-cafe, and then you are humbled.) (I might be talking about the 3 years ago me, here :) ) > You're comparing apples to oranges: using Haskell and understanding the > underlying theory are two completely different > things. Agree 100%, but it's not automatic to see it that way for a newcomer. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskellers design
2010/10/21 Michael Snoyman > > > * How important is adhering to a "standard" look? > Important yet it should not feel like it's impossible to try new things > * Which theme is overall more visually appealing? > 2nd > * Which theme gives a more professional feel? > 2nd David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskellers.com skills list moderation?
2010/10/18 Andrew Coppin : > ...I thought *I* was the only person who's ever heard of Rexx? ... and thanks to you, I now know some people here have heard of Amiga :) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Who is afraid of arrows, was Re: [Haskell-cafe] ANNOUNCE: Haskell XML Toolbox Version 9.0.0
2010/10/13 Henning Thielemann : > David Virebayre schrieb: >> 2010/10/12 Gregory Crosswhite : >> >>> Also, I don't see why one would prefer >>> over the standard function >>> composition operator, ".". >> >> With "." you have to read right-to-left to follow data's path. >> >> For me that reading order isn't natural, and I imagine it is so for >> most people which don't have a mathematical background. > http://www.haskell.org/haskellwiki/Direction_of_data_flow Very informative link, thanks. Fortunately the time when I was struggling with all that is gone; Even though right-to-left still isn't "natural" to me, I've now written enough haskell so that isn't a problem anymore. I don't even try to use >>> redefine a left-to-right composition operator in my programs, I'm converted ! My previous post was just me remembering my (past) problems with "." to answer Gregory's question. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Who is afraid of arrows, was Re: [Haskell-cafe] ANNOUNCE: Haskell XML Toolbox Version 9.0.0
2010/10/12 Gregory Crosswhite : > Also, I don't see why one would prefer >>> over the standard function > composition operator, ".". With "." you have to read right-to-left to follow data's path. For me that reading order isn't natural, and I imagine it is so for most people which don't have a mathematical background. Combined with >>= / >> you have multiple reading direction in the same expression, as in expression ( c . b . a ) `liftM` a1 >>= a2 >>= a3 reading order 6 5 41 2 3 So that could be one reason. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskellers.com recent changes (and I need some volunteers)
2010/10/10 Michael Snoyman : Hi, > Haskellers became popular a lot faster than I'd anticipated. This has I've noticed a new 'flag this user' on my profile, but it's not clear (at least to me) what this does. Out of curiosity, I clicked on it, got a uninformative (again, to me) message "A flag message has been sent to the admins. Thanks!" > easier to add the status. Also, don't take it personally if an admin > denies your "real haskeller" request; it's currently a very poorly > defined notion, and I don't even know who the admins are going to be. I don't like this notion, or at least how it's called. What is supposed to be a real haskeller ? For example, I do use haskell for small things, try to advocate it around me as much as I can, but at the same time I never contributed to a project, or released a package. I don't think I'm worthy of a special status, so I wouldn't ask for "real haskeller" status. At the same time, I don't feel like a fake Haskeller either. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] benchmarking c/c++ and haskell
Does it help to compile with ghc --make -O2 -funbox-strict-fields ?? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Oracle stored procedures
2010/9/7 Peter Marks : > Are there any Haskell libraries that can call stored procedures in Oracle? > I've been looking at Takusen which I like, but I can't find a way to call a > stored procedure. Don't you need to execute a SELECT query that calls the procedure, as in select my_procedure(parameter) Not sure though, I've never used stored procedures. David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Paralelism and Distribution in Haskell
> This is not stupid, but yes you missed something :) > http://www.reddit.com/r/haskell/comments/dad6j/unless_theres_a_major_hiccup_itll_be_in_ghc_70/ Oh, I saw that thread, but at the time it had vrey few comments, so I definately missed something ! Thanks ! David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Paralelism and Distribution in Haskell
2010/9/7 Ben Lippmeier : > Though be warned you must use a recent GHC head build to get good > performance. After GHC 7.0 is out (in a few weeks) we'll be able to release a > properly stable version. Pardon a probably stupid question, but did I miss something ? http://hackage.haskell.org/trac/ghc/roadmap David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: text 0.8.0.0, fast Unicode text support
2010/9/1 Tako Schotanus : > As a Haskell noob I'm curious about this statement, is there something > intrinsically wrong with String? String is just a linked list of Char which are unicode code points; which is probably not the optimal way to store text. For intensive use of text it takes too much memory, and/or it's not fast enough. Sometimes I'd love if I could program using String and the compiler would automatically convert that to Text, or Bytestrings, but of course it's wishful thinking. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Changing my Profile
2010/8/23 Christopher Done : > Any suggestions would be appreciated. Isn't there the possibility to mute a thread in gmail ? You need to activate keyboard shortcuts, then "?" gives you a list of keys. m seems to be used to mute a thread, but I didn't try it so I don't know what it does exactly. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage on Linux
2010/8/24 Ivan Lazar Miljenovic : > What do you mean by "metapackages"? Metapackage are packages of packages, they don't provide something by themselves, but they have a dependency list so that a set of package can be installed together. For example, on ubuntu, installing "build-essentials" will pull gcc, make, autoconf, etc from the repositories. Another example would be the haskell platform, on debian it's a metapackage that depends on all the individual packages of libraries and tools that belong to the platform. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suggestions For An Intro To Monads Talk.
On Fri, Aug 6, 2010 at 5:58 PM, Alex Stangl wrote: > On Fri, Aug 06, 2010 at 10:17:26AM -0500, aditya siram wrote: >> >From my vantage point they are (in no particular order) : Reader, Writer, >> State, IO, ST, STM, Parsec (have I missed any?) and of course the >> transformer versions. I am debating whether or not to add [] to the bunch. > > Not sure how much time you have budgeted, but I'd start with a simple > one like Maybe, actually show how to implement it, then move on to list, I second that. Especially, if the audience is more familiar with imperative langages, then the reader, writer and state monad may not immediately impress them. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preview the new haddock look and take a short survey
On Sat, Aug 7, 2010 at 7:54 AM, Magnus Therning wrote: > Wouldn't the docs be unusable if it were in French even if > Haddock handled unicode characters correctly? Joke aside, for software to be released, a French documentation indeed wouldn't be of much use. The langage of technology and science and les internets is English, and I'm fine with that. I would only document software in French that is written for my company, and isn't supposed to be released. I hope we're not hijacking the thread here :) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preview the new haddock look and take a short survey
I prefer the new look. That being said, I'd rather like haddock handling unicode characters in comments, at the moment it's unusable if I want to write comments in French. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what's the best environment for haskell work?
On Fri, Aug 6, 2010 at 6:11 AM, Hamish Mackenzie wrote: > On 5 Aug 2010, at 21:12, David Virebayre wrote: > Can you try out this... > > ~/haskell/test$ cat ~/bin/cabal_quick_init > #!/bin/sh > > SOURCE_FILE=$1 > CABAL_NAME=`basename -s .lhs $SOURCE_FILE` > CABAL_NAME=`basename -s .hs $CABAL_NAME` > echo Creating Cabal Package $CABAL_NAME > echo For file $SOURCE_FILE > mkdir $CABAL_NAME.package || exit > cd $CABAL_NAME.package || exit > cabal init -n -p $CABAL_NAME --is-executable --source-dir=.. || exit > sed -e "s/-- *[mM]ain-[iI]s *\:/Main-is:$SOURCE_FILE/" -i "" > $CABAL_NAME.cabal || exit This script doesn't word as-is for me. basename doesn't have a -s option, but that's easily corrected. Then, I couldn't get the sed command to work, so I edited manually the cabal file to modify and uncomment the Main-is line. > This will make a Euler/Euler.cabal file. You can then simply add that .cabal > file to your workspace (right click in the Workspace pane). Actually it makes a Euler.package/Euler.cabal file. Minor detail :) > I'll try to fix "leksah Euler.hs" so it does the following > * if the file belongs to an package in the workspace open the file and > activate the package > * if not ask the user if they want to simply open it or cabalize it That would be great. > We do plan to fix this in the same way we resolve missing imports. I had a > look to see if I could do it when a user cabalizes the source, but "ghc > --make -v" does not include the packages automatically loaded in its output. > Instead we will need to wait for the error then resolve it when the user > presses Ctrl+R. Continuing on my Euler.hs example, I then created the cabal package with your script. Added the package, then tried to build. ../Euler.hs:1:0: Failed to load interface for `Prelude': It is a member of the hidden package `base'. Perhaps you need to add `base' to the build-depends in your .cabal file. It is a member of the hidden package `base-3.0.3.2'. Perhaps you need to add `base' to the build-depends in your .cabal file. Use -v to see a list of the files searched for. I didn't find a way to automatically fill the dependencies, Ctrl-R doesn't seem to do something. I added base >= 4 using the package editor, then it build. By the way, did I mention you guys are doing an awesome job with leksah ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why is toRational a method of Real?
On Thu, Aug 5, 2010 at 1:55 PM, Henning Thielemann wrote: > It's even worse: The NumericPrelude is in progress, certainly currently > better than Haskell 98's type classes, but there are known problems. > Sometimes new numeric types are implemented and require to refine or > restructure the classes, again. And there are not only problems with the > numeric type classes, think of Functor, Applicative, Monad, and so on. In my > opinion before trying to move to an improved numerical type hierarchy we > should have class aliases designed, implemented and thoroughly tested in > GHC. > It's sad because the class alias proposal was dropped from Haskell' two years ago, isn't it ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why is toRational a method of Real?
On Thu, Aug 5, 2010 at 1:11 PM, John Meacham wrote: > use. This isn't to say ghc is doing the wrong thing, I don't think there > really is a right thing to do here given the broken class specifications > in the report. I often read that the numerical classes are problematic. At the same time, there are many programs and packages that rely on Haskell being that way. What would it take to redesign the numeric class so that the new design eventually becomes the new Haskell standard ? ( not just an alternative prelude ) Is it doable at all ? Would a first step be trying to compile all of hackage with the numeric prelude and see what breaks ? If it's doable, how many years would it take to make it happen ? Just curious. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why is toRational a method of Real?
On Thu, Aug 5, 2010 at 11:35 AM, Henning Thielemann wrote: > What else shall a rounding function return if not integers? Getting from 29.84645 to 29.85 isn't rounding ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what's the best environment for haskell work?
On Wed, Aug 4, 2010 at 8:01 PM, Hamish Mackenzie wrote: > I use Leksah and have done since I started contributing to it. The best way > to make it work for you is to use Leksah to fix what you don't like about > Leksah ;-) Failing that giving good feedback about bugs and missing features > is the next best thing. I did check the bug/feature tracker, and most issues I have are already there, but with a low priority. I could try to contribute, but I'm both lazy and unsure I can be of help > > On 3 Aug 2010, at 18:48, David Virebayre wrote: >> Trying code completion in comments on string constants, for example. >> Code completion makes the text jump if you're editing near the bottom >> of the editor area. >> I like the "tocandy" feature but then it breaks alignment if you open >> the file in another editor. Something probably fixable by editing the >> candy file. > Just out of interest which of the candy replacements caused problems. Some > of them (such as ->) already are set to include spaces to pad out differences. For example, . Here's an example without, and with candy : listeEtageres = flip zip [1..] -- on les numérote . nub -- on élimine les doublons . sort-- on les trie . map simple -- on ne garde que le type et la position $ listeEtagTot-- on part de la liste totale des étagères where simple (_arm,tpe,pos) = (tpe,pos) f n (t,p) = (n,t,p) listeEtageres = flip zip [1..] -- on les numérote ∘nub -- on élimine les doublons ∘sort-- on les trie ∘map simple -- on ne garde que le type et la position $ listeEtagTot-- on part de la liste totale des étagères where simple (_arm,tpe,pos) = (tpe,pos) f n (t,p) = (n,t,p) --- > Does your existing editor handle candy better? If so how? It doesn't handle them at all :) > Thanks for the feedback, please let us know if you think of anything else. This is an example of how i'm confused. In this example, I'm trying to load a single file. It's for test purposes only, I only need it made by ghc --make, I don't need a cabal package. $ cd code/euler $ leksah Euler.hs leksah loads with my previous package loaded. Here, I hoped it'd open the file I mentionned on the command line. Now, I need to close the package or workspace I'm working on, but I'm not sure which. as there's no such option in the Package menu, I suppose I have to close the workspace. I close it, but my source file remains open. I close it. Since I want to see if 'leksah file' works, I close leksah and I'm back at the shell. $ leksah Euler.hs I back again in leksah, this time with no package/workspace opened, but my Euler.hs file did not open either. back to the shell again $ leksah -v Leksah the Haskell IDE, version 0.8.0.6 $ leksah --help Leksah the Haskell IDE Usage: leksah [OPTION...] files... -v--version Show the version number of ide -l NAME --loadSession=NAME Load session -h--help Display command line options -e Verbosity --verbosity=Verbosity One of DEBUG, INFO, NOTICE, WARNING, ERROR, CRITICAL, ALERT, EMERGENCY According to this help, I should be able to give it a file on the commande line, but it seems it does nothing. No message to tell me what's wrong. Also, there's an option to load a session. What's a session ? the IDE tells of workspace and package, how is that related to sessions ? anyway, back to leksah. I open my file Euler.hs. I can't seem to use the browser if I don't define a package. I click several times the menu Package->New package, but nothing happens I click also Package->Edit package. After a few clicks, I try Package->Edit flags and leksah exits without warning. On the shell, I see -- Needs an open workspace Needs an open workspace No active package to edit Needs an open workspace Needs an open workspace No active package to edit leksah: Can't get pane ***lost connection ***lost last connection - exiting leksah-server: ExitSuccess ***lost last connection - waiting ExitSuccess So I understand why the package menus didn't work, but there was no alert while I was in leksah. And it did crash when I clicked on Package->Edit flags (reproductible) Now I create a workspace since I have to. On the browser I still don't have access to my file. Make workspace does nothing, and tells me nothing. I suspect I need a package. So I'm creating a package. When I click save, it creates a Main.hs file for me. Right now I'm kind of annoyed, I just wanted to edit Euler.hs, add another probl
Re: [Haskell-cafe] what's the best environment for haskell work?
On Mon, Aug 2, 2010 at 4:12 PM, Phyx wrote: >> I've tried to use leksah but some minor annoying things make it unusable for >> me. > I'm curious, what are those minor annoying things? Trying code completion in comments on string constants, for example. Code completion makes the text jump if you're editing near the bottom of the editor area. I like the "tocandy" feature but then it breaks alignment if you open the file in another editor. Something probably fixable by editing the candy file. I'am a bit lost between Workspace and Package, especially when all I want is write a quick single-source haskell program. That's all I can think of right now, I've exagerated a bit when I said "unusable". Leksah is going to be an awesome editor, it's just not ready yet for me. David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what's the best environment for haskell work?
On Sat, Jul 31, 2010 at 12:07 PM, Rustom Mody wrote: > Do most people who work with haskell use emacs/vi/eclipse or something > else?? I mostly use kate, with a separate terminal window running ghci. I've tried to use leksah but some minor annoying things make it unusable for me. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is 'flip' really necessary?
On Sun, Jul 25, 2010 at 11:53 PM, Edward Z. Yang wrote: > An interesting alternate spin on flip is infix notation combined with partial > application, such as: > > (`foobar` 3) > > which is equivalent to > > \x -> foobar x 3 > > I frequently use this, although the jury's out on whether or not it's more > readable. I had HLint suggest me this : before : listeEtagTot = concatMap (flip listeEtagArm cfgTypesTringle) listeArmOrd after : listeEtagTot = concatMap (`listeEtagArm` cfgTypesTringle) listeArmOrd David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Newbie] What to improve in my code
On Tue, Jul 13, 2010 at 11:49 PM, Frank1981 wrote: > > First of all: I'm not sure if this question is allowed here. If not, I > apologize > > I'm trying to solve the following problem: For each word in a text find the > number of occurences for each unique word in the text. > > i've come up with the following steps to solve this: > * remove all punctuation except for whitespace and make the text lowercase A minor point: instead of removing the punctuation, you maybe should convert it to whitespace. Otherwise in texts like "there was a quick,brown fox" (notice the missing space after the comma) you'll have the word "quickbrown" instead of 2 words "quick" and "brown". David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is Haskell unsuitable for?
On Tue, Jul 6, 2010 at 9:23 PM, Yves Parès wrote: >> I must have the same impediment. We should start a support group, that, or >> give in and write a compiler. To add insult to injury, >> I think it should be called "Turbo Haskell". > > That's true... I never noticed, because in French the two words get > pronounced very differently. Indeed. Sadly, I almost never get to speak about Haskell in French... Except when I'm advocating it to my friends. There's a majority of words I learned with haskell I have no idea what their translation is in French. For others, the direct translation sounds horrible "Haskell est un language fainéant". I'm lucky I like English. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suggestions for an MSc Project?
On Sun, Jul 4, 2010 at 10:43 AM, John Smith wrote: > My MSc requires a project dissertation, which is expected to take about 800 > hours. I would like to work on something which is of use to the Haskell > community. Any suggestions? I'd love to see something like git-gui for darcs. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How does one get off haskell?
2010/6/17 Günther Schmidt : > Anyway the problem is that I am totally reluctant to code in anything else > but haskell. It has always been a problem to me getting up early in the You're not alone. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is Haskell unsuitable for?
On Thu, Jun 17, 2010 at 3:38 PM, Henning Thielemann wrote: > On Wed, 16 Jun 2010, Marc Weber wrote: >> Hi Aditya Siram, >> - maybe shell scripting: running ghci takes longer than starting bash. >> Compiling is not always an option because executables are bigger than >> shell scripts or C executables > Is Hugs better in this respect? Or JHC ? JHC's executables are small. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is Haskell unsuitable for?
On Wed, Jun 16, 2010 at 11:04 AM, Ivan Lazar Miljenovic wrote: > David Virebayre writes: >> *Real* programmers use butterfiles [1]. > If your files are composed of butter, I"d hate to see how you store them > in an efficient manner... Oh well, at least le ridicule ne tue pas(1)... I'm a typo specialist. (1) Being ridiculous doesn't kill :) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is Haskell unsuitable for?
On Wed, Jun 16, 2010 at 8:00 AM, Michael Snoyman wrote: >> Next you'll say there's no need for anyone to ask whether they prefer >> vi or emacs... ;-) > Of course *real* programmers use ed. It is the standard editor[1]. *Real* programmers use butterfiles [1]. [1] http://xkcd.com/378/ David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: how to get end location
On Mon, Jun 14, 2010 at 12:10 AM, Roman Cheplyaka wrote: > Of course most parsers don't consume trailing newlines. But I was > writing general function to use in many places in the code which would > recover the end location. In most cases it just subtracts 1 from the > column number, but what if it just happened so that column number is 1? Parsec can handle state, right ? You could modify the parsers for white space so they record the beginning position in some state. ( In a maybe ) Then, modify parseWithLocation to set the state position to nothing, parse p then if no position has been recorded in the state , use the current position, else use the position in the state. Excuse me if this is unclear or confused, it's late :) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] is there a way to prove the equivalence of these two implementations of (Prelude) break function?
On Sun, Jun 6, 2010 at 5:10 AM, Thomas Hartman wrote: > Here's two implementations of break, a snappy one from the prelude, ... > prelbreak p xs = (takeWhile (not . p) xs,dropWhile (not . p) xs) -- > fast, more or less as implemented in prelude iiuc I had a look at the prelude, and I was surprised to see there's 2 versions, depending on a flag : #ifdef USE_REPORT_PRELUDE break p = span (not . p) #else -- HBC version (stolen) break _ x...@[] = (xs, xs) break p xs@(x:xs') | p x= ([],xs) | otherwise = let (ys,zs) = break p xs' in (x:ys,zs) #endif I'm curious why is it so, and which version is compiled in the platform or the ghc binaries. ( my guess is USE_REPORT_PRELUDE compiles functions as defined in the haskell report, but the other version is faster and used by default. ) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH wrote: > You might want to reread that license agreement. Specifically: > > "Applications must be originally written in Objective-C, C, C++, or > JavaScript as executed by the iPhone OS WebKit engine, and only code > written in C, C++, and Objective-C may compile and directly link > against the Documented APIs (e.g., Applications that link to > Documented APIs through an intermediary translation or compatibility > layer or tool are prohibited)" Ah, yes. Ouch, that's abusive. Can they tell the difference though ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 9:23 AM, Lyndon Maydwell wrote: > As a side note, how is this project getting around the language > restrictions apple put in the developer license agreement? >From the project page : This version uses Apple's official iPhone SDK as its back end compiler. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why cannot ghc find a existng module ?
On Tue, May 11, 2010 at 10:10 AM, zaxis wrote: > `ghc-pkg list` finds two random packages. After `ghc-pkg unregsiter` the one > installed by cabal in ~/.ghc/, all works normally now! I stopped counting the number of times I've reinstalled GHC because I forgot to tell cabal to install a package globally. I really should modify the config file. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
By the way, I didn't exactly reply your question : > [...] Basically, i don't understand what does "ErrorT ::" means - it > should name the function - but it starts with capital letter? It's a type signature, it describes the type of ErrorT: Prelude> import Control.Monad.Error Prelude Control.Monad.Error> :t ErrorT ErrorT :: m (Either e a) -> ErrorT e m a So that says, ErrorT is a value constructor that takes a value of type m (Either e a) and makes a value of type ErrorT e m a. Notice that the type constructor and the value constructor have both the same name ErrorT, I used to get confused by this when I began learning. If you type under ghci Prelude Control.Monad.Error> :k ErrorT ErrorT :: * -> (* -> *) -> * -> * That tells you that ErrorT is a type constructor that takes a type, a unary type constructor, and a type; and with all this defines a new type (ErrorT e m a). David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
On Thu, May 6, 2010 at 9:56 AM, Eugene Dzhurinsky wrote: > On Wed, May 05, 2010 at 02:54:27PM -0700, Ryan Ingram wrote: >> ErrorT is just a newtype wrapper, changing the order/application of >> the type variables. >> >> newtype ErrorT e m a = ErrorT (m (Either e a)) >> runErrorT (ErrorT action) = action >> >> This gives the bijection: >> >> ErrorT :: m (Either e a) -> ErrorT e m a >> runErrorT :: ErrorT e m a -> m (Either e a) > > That syntax is not clear for me - so ErrorT is some sort of function > (calculation), which takes a monad with type (Either e a) and produces type > ErrorT e m a ? Basically, i don't understand what does "ErrorT ::" means - it > should name the function - but it starts with capital letter? A constructor can be seen as a function that takes some parameters and produces a value for example with the type Maybe a, which has 2 constructors ; Just and Nothing : Prelude> :t Just Just :: a -> Maybe a the constructor Just is a function that takes a value of type a and makes a value of type Maybe a. Prelude> :t Just Just :: a -> Maybe a David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Weekly News?
On Wed, Apr 28, 2010 at 7:47 AM, David Sankel wrote: > I'm wondering if a monetary incentive would keep the person who does this > work more accountable. I personally would be willing to contribute to > continue getting this service. I wonder if there are others as well. I don't think money would be an incentive for someone that has "7 classes worth of finals and papers" to do Now a time machine. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compressing GHC tarballs with LZMA
>> How common is support for .xz on the platforms we are interested in here? > Not very. dpkg may support it in the future, but that is a somewhat closed > platform where Debian folks are in charge of both the archive and the tool > used to unpack it. Trying to install xz on kubuntu brings a serious warning : The following packages will be REMOVED: lzma The following NEW packages will be installed: xz-utils WARNING: The following essential packages will be removed. This should NOT be done unless you know exactly what you are doing! lzma (due to dpkg) 0 upgraded, 1 newly installed, 1 to remove and 8 not upgraded. Need to get 173kB of archives. After this operation, 233kB of additional disk space will be used. You are about to do something potentially harmful. To continue type in the phrase 'Yes, do as I say!' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Hackage accounts and real names
And another +1 from me too. Keeping the policy will only achieve that people who want to stay anonymous will stay away from hackage, and that's not something (IMHO) we should want. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackape package lackage
On Mon, Mar 22, 2010 at 5:31 PM, Thomas Davie wrote: > I'd love to see that map normalised by the population of the country – would > be interesting to see where Haskell is popular. Looks like it's very very popular in Alaska :-) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: If wishes were horses... (was: Re: definition of sum)
On Fri, Mar 12, 2010 at 12:01 PM, Johannes Waldmann wrote: > David Virebayre gmail.com> writes: > in this case, something like: Data.List.Strict.fold, Data.List.Lazy.fold But then if you need both version, you will have to import them qualified, which I don't like much. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: If wishes were horses... (was: Re: definition of sum)
On Fri, Mar 12, 2010 at 10:29 AM, Johannes Waldmann wrote: > Well, meaningful identifier names is nice, but I think > here we have a case of the code smell "type info embedded in the name". > Strictness of a function should be expressed in the function's type instead. > But that seems impossible with Haskell at the moment. > (At best, we can express strictness of constructors?) > Hence we have "underspecified" behaviour: > > Prelude Data.List> :t foldl' > foldl' :: (a -> b -> a) -> a -> [b] -> a > > Prelude Data.List> :t foldl > foldl :: (a -> b -> a) -> a -> [b] -> a Even if we had a syntax to express that the function is strict, wouldn't we still need two distinct function names for the strict and lazy case ? In that case, some sort of convention on naming is nice, because if I want to change a function to its strict version, I know there's a good chance it's the one that ends with a ' David. > > and need to resort to the awkward workaround via naming conventions. > > Of course Haskell implementations do have some kind of strictness > information (e.g., in ghc interface files), so it's not impossible > to define some kind of annotation system. > > Although I did not check what the compiler's strictness info is > for foldl and fold' - and what was actually needed (at the source level). > The current textual definition (Data.List API docs: "foldl' = a > strict version of foldl") is not too precise, either. > > Well, I guess there's a huge design space. But it's a huge problem > (describing/controlling the behaviour of lazy programs). > > Best - J.W. > > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenSUSE 11.2
On Sun, Feb 28, 2010 at 6:30 PM, Andrew Coppin
wrote:
> Daniel Fischer wrote:
>
> if [ -z `/bin/echo ${PATH} | /usr/bin/grep cabal` ]
>
> then
>>export PATH="/home/andrew/.cabal/bin:$PATH"
>> fi
>>
>> in your .bashrc
>>
>>
>
> Uh... what?
that snippet supposes you have cabal installed in your home directory under
the directory ".cabal". The binary file would be in the bin subdirectory of
".cabal"
Names that start with a . are hidden files/directories on linux, by the way.
So the first line checks if you have "cabal" in your path list. If not, on
the 3rd line it supposes your home directory is /home/andrew and adds the
cabal binary directory to your path list.
David.
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Re: [Haskell-cafe] wildcards for type variables?
On Wed, Jan 13, 2010 at 12:29 AM, Evan Laforge wrote: > Occasionally I have a function with an unused argument, whose type I > don't want to restrict. Thus: > > f :: _unused -> A -> B > f _ a = b I probably misunderstood the problem, why not f:: a -> A -> B David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Are functional dependencies around to stay?
2009/12/21 Günther Schmidt > Hi everyone, > > I'm wondering if there is any chance that functional dependencies will not > be around in the future. I do not actually understand the subject yet as > such, but I'd like to make sure before I get deeper into it that it's > something that will be around in the time to come. > My understanding is that they might end up dropped in favor of type families, and that should happen about when chicken will start growing teeth. Obviously, my understanding is probably flawed. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Zumkeller numbers
On Wed, Dec 9, 2009 at 11:47 AM, Henning Thielemann wrote: > Ist der Ruf erst ruiniert, lebt es sich ganz ungeniert. 8-] > Is there an English translation of it? Google translate says : "If the reputation is ruined, one can live quite openly." David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is Haskell a Fanatic?
On Fri, Dec 4, 2009 at 10:34 AM, Simon Peyton-Jones wrote: > Friends Amen ! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Optimization with Strings ?
On Thu, Dec 3, 2009 at 1:03 PM, Emmanuel CHANTREAU wrote: > In my futur program, it use a lot of binary trees with strings (words) > as leaf. There is just arround 1000 words and they will appear a lot of > times. The program will possibly consume a lot of process and memory > (it is a mathematics proover). > I began this program in C++ but haskell has a prety good speed and > memory footprint and is easier. But I don't know if it worth to do this > optimization: having a dictionary to translate string words in Int. > The answer depends on the automatic optimizations in GHC, because GHC > could compare quickely two strings if it is the same object, so it > depends if program generated by GHC have a dictionary (tree) of strings > internaly. Someone knows this ? It doesn't work this way : Strings are just lists of Chars. Comparison is made recursively, Char by Char. You can have a look at the source to make sure : instance (Eq a) => Eq [a] where [] == [] = True (x:xs) == (y:ys) = x == y && xs == ys _xs== _ys= False So you will have to code your own optimisation. David. P.S. In French if you didn't understand: Ca ne marche pas comme ça. Les chaines de caractères ne sont que des listes de caractères. La comparaison sur les listes est faite récursivement, caractère par caractère, il suffit pour s'en assurer de regarder au source : Donc il vaut mieux que tu implémente ton propre dictionnaire. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Typeclasses for name punning (was: Re: I miss OO)
2009/11/27 Daniel Schüssler > > I think punning is a worthwhile goal on its own, since I find myself > wasting > quite some thought on whether to prefix a record field name somehow, and if > I > do, what I should use as a short but sufficiently unique prefix. > I agree, especially since it looks like the record situation is not about to be solved; for example by looking at the discussion generated by Simon Peyton-Jones's TDNR proposal (which I like, but I don't feel like my opinion should count on that matter ) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What does the `forall` mean ?
On Thu, Nov 12, 2009 at 8:52 PM, Andrew Coppin wrote: > I just meant it's not immediately clear how > foo :: forall x. (x -> x -> y) > is different from > foo :: (forall x. x -> x) -> y > It takes a bit of getting used to. That still confuses me. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Resource compilation in GHC
On Thu, Nov 12, 2009 at 11:12 AM, Konstantin Vladimirov wrote: > Hello. > I'm writing an wxHaskell application. Everything is ok, but now I need > a separate folder for icons, bitmaps, and so on, from where they are > loaded at runtime. How can I compile resources, and link them into my > executable to provide for users single .exe file with resource section > inside it? +1 ! I would also like to know how one can do it with gtk2hs. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Static Linking Problem
On Wed, Nov 11, 2009 at 5:44 PM, Svein Ove Aas wrote: > My recommendation would be to take glibc off the list of statically > linked libraries. How do you do that ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] faster compiling for ghc
On Thu, Nov 12, 2009 at 7:18 AM, Bulat Ziganshin wrote: > > Hello Evan, > > Thursday, November 12, 2009, 4:02:17 AM, you wrote: > > > Recently the "go" language was announced at golang.org. There's not a > > lot in there to make a haskeller envious, except one real big one: > > compilation speed. The go compiler is wonderfully speedy. > > are you seen hugs, for example? i think that ghc is slow because it's > written in haskell and compiled by itself If I understood, Evan is interested in ideas to speed up compilation. As far as I know, hugs is an interpreter, not a compiler. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What's the deal with Clean?
On Fri, Nov 6, 2009 at 8:45 AM, Ketil Malde wrote: > > enough about. I'd be happy to hear any suggestions. > This is more a question than a suggestion, but would the iteratees package fit your needs ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hoogle is great but ...
On Sun, Oct 25, 2009 at 2:09 PM, Curt Sampson wrote: > But zaxis, here's another thing to look at. There's usually a "view > source" link beside most of the functions that come up in the Haddock > documentation to which Hoogle links. It's worth clicking. You would be > surprised (certainly I was!) at how often looking at the definition > of a function suddenly makes it quite clear what it does, when the > description didn't quite do it for you. (This is one of the joys of > Haskell.) I tried that with parsec 3, my brain exploded :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] x -> String
On Fri, Oct 16, 2009 at 8:19 PM, Andrew Coppin wrote: > Is there any way that you can turn an arbitrary Haskell value into a string? > I rephrase: There *is* a way to turn arbitrary values into strings. I know > there is, because the GHCi debugger *does* it. The question is, does anybody > know of an /easy/ way to do this? Ghci only displays values with a Show instance. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] GHC devs
On Wed, Oct 14, 2009 at 11:06 PM, Bulat Ziganshin wrote: > Hello Andrew, > > Thursday, October 15, 2009, 12:54:37 AM, you wrote: > >> Does anybody actually "get paid" to develop GHC? Or is this all people > > SPJ, SM and Ian are paid by MS Research. Other people involved in core > development are mainly scientists (afaik) Taking the opportunity to thank very much both Simons and Ian for the work they do and the enthusiasm they show. You guys rock. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] better way to do this?
On Wed, Oct 7, 2009 at 10:05 AM, Peter Verswyvelen wrote: > over every bit of the system (it was even easy to count exactly how many > cycles a routine would take :-), so it was just a matter of starting the You sound like you used to code on the Commodore 64 :) David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Curried function terminology
On Mon, Oct 5, 2009 at 11:52 AM, Jon Fairbairn wrote: > [1] A pet peeve of mine is "x supports y" being used backwards (as in > "our application supports windows Vista", which would only make sense if > it were something like a system tool that stopped Vista crashing. (Not a native English speaker here) How would you say "x works well with y" ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
