I could not resist this. The code
import Text.ParserCombinators.UU.Parsing
pCommand [] = pure []
pCommand xxs@(x:xs) = ((:) $ pSym x * pCommand xs) `opt` xxs
pCommands = amb . foldr (|) pFail . map pCommand $ [banana,
chocolate, frito, fromage]
t :: String - ([String], [Error Char Char
You can help ghci out a bit with type synonyms:
type T a = (a, a)
type T2 a = T (T a)
type T4 a = T2 (T2 a)
type T8 a = T4 (T4 a)
type T16 a = T8 (T8 a)
f0 :: a - T a
f1 :: a - T2 a
f2 :: a - T4 a
f3 :: a - T8 a
f4 :: a - T16 a
f0 x = (x,x)
f1 = f0 . f0
f2 = f1 . f1
f3 = f2 . f2
f4
On Wednesday 14 October 2009 5:25:10 am Roel van Dijk wrote:
With newtypes I can probably abstract even more. (newtype X a b = X (a (a
b))
In fact, with GHC extensions, you don't need newtypes:
{-# LANGUAGE LiberalTypeSynonyms #-}
type T a = (a,a)
type X f a = f (f a)
f0 :: a - T
On Wed, Oct 14, 2009 at 11:53 AM, Dan Doel dan.d...@gmail.com wrote:
In fact, with GHC extensions, you don't need newtypes:
{-# LANGUAGE LiberalTypeSynonyms #-}
Ah, I completely forgot about that language extension. Thanks!
Yeah. Asking for the type of 'f4 . f4' doesn't seem to expand the
Dear friends,
It is my pleasure to announce the formation of fp-southwales, a user
group for anybody interested in functional programming in the area of
south Wales, UK. We're based out of Swansea University's Computer
Science department, where there are a few of us using Haskell for our
On Wednesday 14 October 2009 6:15:11 am Roel van Dijk wrote:
If you declare a type for f5 then ghci must check if that type is
correct, which triggers the explosion. If you don't declare a type
then it won't infer the type until necessary. Basically, ghci is lazy
Well, that may be the
So i was reading Programming Game AI by Example by Mat Buckland
(http://www.ai-junkie.com/books/toc_pgaibe.html) and decided to rewrite
his chapter on Fuzzy logic in haskell (from C++).
My initial impression: its one of those scenarios where OOP grossly over
complicates things
Heres an
Nice, thank you for the great work.
Browsing the reverse dependencies of popular packages like bytestring
http://bifunctor.homelinux.net/~roel/cgi-bin/hackage-scripts/revdeps/bytestring-0.9.1.5
can be improved a bit.
1) Can you please sort the reverse dependent package names? That makes it
On Wed, Oct 14, 2009 at 3:24 PM, hask...@kudling.de hask...@kudling.de wrote:
Nice, thank you for the great work.
Browsing the reverse dependencies of popular packages like bytestring
http://bifunctor.homelinux.net/~roel/cgi-bin/hackage-scripts/revdeps/bytestring-0.9.1.5
can be improved a
My fix would be to parse as many letters as possible many1 alpha
(that's longest match) and then check the result with isPrefixOf for
all your alternatives (and return the alternative that matches first).
Cheers Christian
Martijn van Steenbergen wrote:
Brandon S. Allbery KF8NH wrote:
My fix
On Friday 09 October 2009 07:07:21 pm Duncan Coutts wrote:
On Fri, 2009-10-09 at 17:37 +0200, Sönke Hahn wrote:
Hi!
I need to set an environment variable from Haskell and i would like to do
that cross-platform. There is System.Posix.Env.setEnv, which does
exactly, what i want on Linux.
On Friday 09 October 2009 07:19:30 pm Peter Verswyvelen wrote:
Mmm, that seems like a shortcoming.
Well, you could just wrap the C functions yourself, like this (two
possibilities, no error checking yet, quick hack):
http://hpaste.org/fastcgi/hpaste.fcgi/view?id=10565#a10565
Note that
Can someone give me an example of Sound.PortMidi use? I'm having trouble.
This program has bugs---makes sound only intermittently, and seems to have
set up some kind of loop that is sending midi messages continuously even
after terminating the program:
import Sound.PortMidi
import Foreign.C
Random question of the day: How many developers are working on GHC?
I had always *assumed* that there was something like a hundred core
developers, with a much larger number of people casually testing and
occasionally submitting the odd patch or two.
However, I watched a video of a talk the
Dear café,
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ImpredicativeTypes #-}
type Void = forall a. a
newtype Mono a = Mono { runMono :: [Void] }
beep :: Mono a - Mono a
beep (Mono vs) = Mono (map undefined vs)
Compiling this with GHC results in:
Monotype.hs:9:28:
Cannot match a
I think the contributors page on GHC's wiki contains relevant information:
http://hackage.haskell.org/trac/ghc/wiki/Contributors
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Hello Andrew,
Wednesday, October 14, 2009, 10:28:45 PM, you wrote:
I had always *assumed* that there was something like a hundred core
developers
only 10 and only in binary system :)))
Simon Peyton-Jones works on front-end, i.e compiling Haskell down to
simple core language, and Simon Marlow
On Wed, Oct 14, 2009 at 7:33 AM, o...@okmij.org wrote:
Martin Sulzmann wrote:
Undecidable instances means that there exists a program for which
there's
an infinite reduction sequence.
I believe this may be too strong of a statement. There exists patently
terminating type families that
On Wed, 14 Oct 2009, Michael Mossey wrote:
Can someone give me an example of Sound.PortMidi use? I'm having trouble.
This program has bugs---makes sound only intermittently, and seems to have
set up some kind of loop that is sending midi messages continuously even
after terminating the
bulat.ziganshin:
Hello Andrew,
Wednesday, October 14, 2009, 10:28:45 PM, you wrote:
I had always *assumed* that there was something like a hundred core
developers
only 10 and only in binary system :)))
Simon Peyton-Jones works on front-end, i.e compiling Haskell down to
simple
-- Why does replicateM (10^6) $ return 0 produce output in the IO
monad, but overflow the maybe monad?
iterateNTimes i f x = foldr (.) id (replicate i f) $ x
tntIO :: IO Int
-- same as replicateM (10^6) $ return 0, same as sequence . replicate
(10^6) $ return 0
tntIO = return . head =
Dimitry,
I *believe* ext-core will match that document, but I'm not sure of the
exact status. Tim Chevalier has done a lot of great work maintaining
the external core stuff and I think he is actively using the extcore
library, so *that* should almost certainly match GHC's output.
It's great to
On Wed, Oct 14, 2009 at 10:28 PM, Max Bolingbroke
batterseapo...@hotmail.com wrote:
Dimitry,
I *believe* ext-core will match that document, but I'm not sure of the
exact status. Tim Chevalier has done a lot of great work maintaining
the external core stuff and I think he is actively using the
Don Stewart wrote:
bulat.ziganshin:
Hello Andrew,
Wednesday, October 14, 2009, 10:28:45 PM, you wrote:
I had always *assumed* that there was something like a hundred core
developers
only 10 and only in binary system :)))
About 1000 people have worked on libraries on
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)
--
Best regards,
Bulat
Hello café,
I've never written an Alternative instance for a newtype yet that
doesn't look like this:
instance Alternative T where
empty = T empty
T x | T y = T (x | y)
Why does newtype deriving not work for Alternative? (It works fine for
Monoid.)
Thanks,
Martijn.
Hallo Daniel,
can you explain the difference between a pattern binding and a function
binding? I haven't heard about these two terms so far. And furthermore: Why
does the memoization only happen with pattern binding?
Best regards,
Simon
--
View this message in context:
* Martijn van Steenbergen mart...@van.steenbergen.nl [2009-10-14
20:35:06+0200]
Dear café,
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ImpredicativeTypes #-}
type Void = forall a. a
newtype Mono a = Mono { runMono :: [Void] }
beep :: Mono a - Mono a
beep (Mono vs) = Mono (map undefined
Works for me on GHC6.10.4:
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module NewtypeDerive where
import Control.Applicative
newtype Foo f a = Foo (f a) deriving (Functor, Applicative, Alternative)
newtype Bar a = Bar [a] deriving (Functor, Applicative, Alternative)
-- ryan
On Wed, Oct 14,
You guys are right. I was being silly. Thanks. :-)
Ryan Ingram wrote:
Works for me on GHC6.10.4:
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On Wednesday 14 October 2009 04:50:56 pm Sönke Hahn wrote:
On Friday 09 October 2009 07:19:30 pm Peter Verswyvelen wrote:
Mmm, that seems like a shortcoming.
Well, you could just wrap the C functions yourself, like this (two
possibilities, no error checking yet, quick hack):
It doesn't work for this one:
newtype Split a = Split { runSplit :: [Either a (Char, Split a) ]}
But my handwritten instance remains identical.
Groetjes,
Martijn.
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Am Mittwoch 14 Oktober 2009 23:30:05 schrieb SimonK77:
Hallo Daniel,
can you explain the difference between a pattern binding and a function
binding? I haven't heard about these two terms so far.
The formal specification is at
http://haskell.org/onlinereport/decls.html#sect4.4.3
A function
I didn't read the book, but your code seems very elegant, more than I even
thought possible. I've never programmed with fuzzy logic before, but I can
understand your code - it reads naturally.
Fernando Henrique Sanches
On Wed, Oct 14, 2009 at 9:59 AM, Neal Alexander relapse@gmx.com wrote:
bulat.ziganshin:
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)
Besides MSR and the
Martijn van Steenbergen wrote:
It doesn't work for this one:
newtype Split a = Split { runSplit :: [Either a (Char, Split a) ]}
But my handwritten instance remains identical.
The instance has the form [], not the form [Either _ (Char, Split _)].
Since they don't match exactly, it won't
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