[Haskell-cafe] map/reduce example
Hello Haskell-Cafe,
i've written small program which demonstrates how map/reduce may be
implemented in Haskell. it counts amount of words in file, splitting
it into 64kb blocks processed by two threads. their results are
combined by another two threads. how it may be made better? in
particular, is it strict in values send over channels?
{-# LANGUAGE BangPatterns #-}
import Control.Concurrent
import Control.Concurrent.Chan
import Control.Monad
import Data.IORef
import Data.ByteString.Char8 as B hiding (length)
import System.Environment
import System.IO
main = do
(file:_) - getArgs
h - openBinaryFile file ReadMode
map- newChan
reduce - newChan
result - newChan
replicateM_ 2 (forkIO$ mapThread map reduce)
replicateM_ 2 (forkIO$ reduceThread reduce result)
jobs - new 0
untilM (hIsEOF h) $ do
str - B.hGet h 65536
writeChan map str
jobs += 1
jobs' - val jobs
writeChan reduce (0,-jobs')
res - readChan result
print res
mapThread map reduce =
forever $ do
str - readChan map
let !sum = length (B.words str)
writeChan reduce (sum,1)
reduceThread reduce result =
forever $ do
(sum1,n1) - readChan reduce
(sum2,n2) - readChan reduce
let (!sum,!n) = (sum1+sum2,n1+n2)
case n of
0 - writeChan result sum
_ - writeChan reduce (sum,n)
untilM cond action = do
deny - cond
unless deny $ do
action
untilM cond action
forever action = action forever action
infixl 0 =:, +=
new = newIORef
val = readIORef
a=:b = writeIORef a b
a+=b = modifyIORef a (\a-a+b)
--
Best regards,
Bulat mailto:[EMAIL PROTECTED]
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[Haskell-cafe] Re: is there a more concise way to generate helper functions for a datatype built on records?
Neil Mitchell wrote:
Hi
Some of these can be automatically derived by the Data.Derive tool...
The derivations Set, Is, From, Has, LazySet all look useful.
...
On Nov 24, 2007 4:01 PM, Thomas Hartman [EMAIL PROTECTED] wrote:
I think I'm running into more or less the same issue discussed at
http://bloggablea.wordpress.com/2007/04/24/haskell-records-considered-grungy/
Just wondering if I missed anything, or if any of the ideas
considering better records setter/getters have been implemented in
the
meantime.
Hi,
the Ref deriviation (included in Data.Derive) seems to be a good way
to solve some aspects
of this problem; I have some questions on my own though.
Here is a working example of updating the two player's state in the
pong game:
{-# OPTIONS -cpp #-}
{-# OPTIONS_DERIVE --output=file.h #-}
module Main where
import Control.Arrow
#include file.h
Refs as in (http://www.haskell.org/pipermail/haskell-cafe/2007-June/026477.html
):
type Upd a = a - a
data Ref cx t
= Ref { select :: cx - t , update :: Upd t - Upd cx }
(@.) :: Ref a b - Ref b c - Ref a c
a @. b
= Ref { select = select b . select a,
update = update a . update b }
The game model:
data Object2D
= Object2D { x :: Double, y :: Double } deriving (Show {-! Ref !-})
data Player
= Player { points :: Int, pos :: Object2D } deriving (Show {-!
Ref !-})
data Game
= Game { p1 :: Player, p2 :: Player, ball :: Object2D } deriving
(Show {-! Ref !-})
sampleGame :: Game
sampleGame = Game { p1 = Player 0 (Object2D 5 0), p2 = Player 0
(Object2D 5 10), ball = Object2D 5 5 }
Game update proceeds in several steps, we now consider the first one:
Updating the 2 player's position - this happens, at least
conceptually, *in paralell*
(for example: both players might be aloud to have a look at the other
players position in the last turn, but
not at the updated position).
Here's the update for one player:
updatePlayerPos :: Bool - Upd Player
updatePlayerPos moveRight
= update (refPos @. refX) $
case moveRight of
True - ((min 10) . (+1))
False - ((max 0) . (+(-1)))
If sequential update is ok for us, the game state update is simply:
updatePositions :: Bool - Bool - Upd Game
updatePositions move1 move2 = update refP1 (updatePlayerPos
move1) . update refP2 (updatePlayerPos move2)
To get it *actually* work in parallel we have to create a new
reference for both players:
refPlayers :: Ref Game (Player,Player)
refPlayers = Ref { select = select refP1 select refP2,
update = \pu g - let (p1',p2') = pu (p1 g, p2
g) in g { p1 = p1', p2 = p2' } }
While the select part of the Ref is expressed using , I don't know
how the
paralell update can be expressed in terms of combinators. Any hints ?
Now, the game state update in the parallel version is easy. Note that
it would also be possible now
to take one player's position into account when updating the other
player's position:
updatePositionsPar move1 move2 = (update refPlayers) $
updatePlayerPos move1 *** updatePlayerPos move2
So, the Ref deriviation is really nice for sequential updates;
paralell updates on the other hand need some work.
Furthermore, I don't really know how well Refs work if updates
need information on other parts of the state without modifying it.
(e.g. the AI player needs to know where the ball is, but does not
modify the ball).
I'd really appreciate if anyone has some additional clues.
thanks,
benedikt
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Re: [Haskell-cafe] Old editions of The Monad.Reader lost
On 18 Aug 2007, at 20:10, Henk-Jan van Tuyl wrote: Now that all hawiki pages have been removed, we have lost some valuable information. For example The Monad.Reader; on http:// www.haskell.org/haskellwiki/The_Monad.Reader A few people have been asking what has happened to old editions of the Monad.Reader. I'm happy to announce that almost all authors have agreed to the new Haskellwiki license. I have added the .pdf of the very first issue to the Monad.Reader homepage; Shae Erisson was kind enough to set up a wiki hosting the later issues. http://www.haskell.org/sitewiki/images/9/9d/TMR-Issue1.pdf http://www.haskell.org/tmrwiki/ Both are links can be found on the Monad.Reader homepage. If anyone is inclined to port the MoinMoin content to the Haskellwiki format, I'd be happy to provide them with a list of all the authors that have agreed with the new license. Wouter This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Pretty-printing peg solitaire boards
(...)However, I'm doing that because there's a single position which my brother could not solve, and he believes it to be impossible(...) I guess you meant #0# #0# ###0### ### ### ### ### This indeed can not be solved. (...) Actually, I did mean to start with: ### ### ###0### ### ### ### ### and then go to: #0# #0# ### ### ### ### ### My brother's idea is that he can solve any board after you choose the initial peg to be removed and the first move. He can do it for any combination, except for this one. But your argument is very interesting, indeed! I'll try to find that book, we'll like to read it. Best, Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New slogan for haskell.org
On Thu, 4 Oct 2007, Don Stewart wrote: The Haskell website has the rather strange motivational text: Haskell is a general purpose, purely functional programming language featuring static typing, higher order functions, polymorphism, type classes, and monadic effects. Haskell compilers are freely available for almost any computer. To continue an old thread: What about turning the strange words like 'monadic effects' into links to glossary articles? Btw. where is 'lazy' ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New slogan for haskell.org
On Mon, 26 Nov 2007, Thomas Davie wrote: On 26 Nov 2007, at 15:15, Henning Thielemann wrote: On Thu, 4 Oct 2007, Don Stewart wrote: The Haskell website has the rather strange motivational text: Haskell is a general purpose, purely functional programming language featuring static typing, higher order functions, polymorphism, type classes, and monadic effects. Haskell compilers are freely available for almost any computer. To continue an old thread: What about turning the strange words like 'monadic effects' into links to glossary articles? Btw. where is 'lazy' ? I believe the point of this discussion was that anyone reading the Haskell webpage will currently get about as far as featuring static typing, and go this is all very nice, but what exactly does this language do for me? Why should I use it?. Take for example what the python website says: I didn't want to repeat the discussion. I think the discussion ended with: Anything more helpful would be too long for the title line at haskell.org, and a more detailed explanation (but not a generic advertisement like that from Python) should be reachable easily. Now my idea was, that making links to glossary articles leaves the slogan as short as it is, and allows people to find out quickly about the words they still don't know. An explanation why Haskell's features are useful for programmers is still required. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] The Monad.Reader - Call for Copy
Call for Copy The Monad.Reader - Issue 10 I would like to welcome articles for the anniversary issue of The Monad.Reader. * The Monad.Reader * The Monad.Reader is an electronic magazine about all things Haskell. It is less-formal than journal, but somehow more enduring than a wiki- page. There have been a wide variety of articles, including: exciting code fragments, intriguing puzzles, book reviews, tutorials, and even half-baked research ideas. * Submission Details * Get in touch with me if you intend to submit something -- the sooner you let me know what you're up to, the better. Please submit articles for the next issue by e-mail (wss at cs.nott.ac.uk) to me before ** January 25, 2008 ** Articles should be written according to the guidelines available from http://www.haskell.org/haskellwiki/The_Monad.Reader Please submit your article in PDF, together with any source files you used. The sources will be released together with the magazine under a BSD license. If you would like to submit an article, but have trouble with LaTeX please let me know and we'll sort something out. Looking forward to your submission, Wouter This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New demo/test program for Yhc Javascript backend
It would be really helpful if you could include this (and other) examples in an /examples directory under src/translator/js in the yhc darcs distribution, with working makefiles that validate against the buildbot. Something seems a bit off for me, probably forgot a tilde somewheres. t. 2007/11/17, Dimitry Golubovsky [EMAIL PROTECTED]: Hi, For those of you who are interested in using Haskell in client-side web application programming: I have added a new demo/test program to this Wiki page (Does it leak?): http://haskell.org/haskellwiki/Yhc/Javascript This demo program shows some progress made since the first announcement of Yhc Javascript backend (Core to Javascript converter) was made about a year ago. Please test the demo for functionality and memory leaks in various browsers. Your feedback is appreciated. The demo program is self-contained (does not require any Haskell libraries beyond those included with Yhc). There is a darcs repo: http://www.golubovsky.org/repos/wsptest/ from which this demo program along with Makefile can be obtained if anybody wants to play with the code. Thanks. -- Dimitry Golubovsky Anywhere on the Web ___ 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] Re: Pretty-printing peg solitaire boards
Maur??cio wrote: Actually, I did mean to start with: ### ### ###0### ### ### ### ### and then go to: #0# #0# ### ### ### ### ### My brother's idea is that he can solve any board after you choose the initial peg to be removed and the first move. He can do it for any combination, except for this one. Heh. He's in for a surprise, there are actually solutions for this. It was surprisingly hard to find one though. Thanks for the puzzle. (I won't spoil it here. Ask me off list if you're interested.) But your argument is very interesting, indeed! I'll try to find that book, we'll like to read it. It's a series of three books actually. Sadly it's been a long time since I've read them so I forgot which volume covers which topics. Bertram ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] getDirectoryContents still causing problems Re: problems building ycr2js (hopefully fixed)
still having problems darcs pulling your updates, related to System.FilePath. did you make clean and then make again? I darcs pulled everything. (cd src/translator/js; make all install) ... ... (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskell; \ for f in `find . -name '*.hs' | sort` ; do make -s -f /home/thartman/haskell-installs/yhc-install/yhc/src/translat\ or/js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) -s flag silences, we don't want that, with verbose output again we see that make is failing for a huge number of packages (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/h\ askell; \ for f in `find . -name '*.hs' | sort` ; do make -f /home/thartman/haskell-installs/yhc-install/yhc/src/translator/\ js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc --core --no-bytecode CDOM/Level1/DomUtils.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) make: *** [CDOM/Level1/DomUtils.ycr] Error 1 yhc --core --no-bytecode CDOM/Level1/Events.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) ... [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskellyhc --core --no-bytecode CDOM/Level1/DomUtils\ .hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) Unfamiliar with yhc, I couldn't figure out where getDirectory contents is being called from. Grepping at the root, I guess something here is causing problems [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhcgrep -irl getDirectoryContents * Make/Useful.hs inst/bin/yhc src/compiler98/Package.hs src/packages/yhc-base-1.0/System/Directory.hs src/packages/haskell98-1.0/Directory.hs src/tester/Main.hs tests/conformance98/Directory/getDirContents/Main.hs best, thomas. 2007/11/25, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, On Nov 25, 2007 5:50 PM, Thomas Hartman [EMAIL PROTECTED] wrote: Thanks Dmitri, I also had to fix an issue with System.FilePath, there's a message about this on haskell cafe. In fact, takeDirectory is the right replacement for getDirectory in older FilePath. I have pushed this change too. Thanks. -- Dimitry Golubovsky Anywhere on the Web ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: getDirectoryContents still causing problems Re: problems building ycr2js (hopefully fixed)
False alarm. I rm -rf ed yhhc, fresh darcs got the latest yhc, reinstalled yhc, and redid (cd src/translator/js; make all install) and it built. 2007/11/26, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, It looks like this comes from Yhc, not from the Javascript backend. Have you done the full sequence of (starting with clean repo)? darcs get darcs.haskell.org/yhc scons core=1 build scons prefix=... install # whatever your stuff goes, and yhc will be in bin/ from that, and this bin/ should be on your path (cd src/translator/js; make all install) Please let me know where it fails. Thank you. On 11/26/07, Thomas Hartman [EMAIL PROTECTED] wrote: still having problems darcs pulling your updates, related to System.FilePath. did you make clean and then make again? I darcs pulled everything. (cd src/translator/js; make all install) ... ... (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskell; \ for f in `find . -name '*.hs' | sort` ; do make -s -f /home/thartman/haskell-installs/yhc-install/yhc/src/translat\ or/js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) -s flag silences, we don't want that, with verbose output again we see that make is failing for a huge number of packages (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/h\ askell; \ for f in `find . -name '*.hs' | sort` ; do make -f /home/thartman/haskell-installs/yhc-install/yhc/src/translator/\ js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc --core --no-bytecode CDOM/Level1/DomUtils.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) make: *** [CDOM/Level1/DomUtils.ycr] Error 1 yhc --core --no-bytecode CDOM/Level1/Events.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) ... [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskellyhc --core --no-bytecode CDOM/Level1/DomUtils\ .hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) Unfamiliar with yhc, I couldn't figure out where getDirectory contents is being called from. Grepping at the root, I guess something here is causing problems [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhcgrep -irl getDirectoryContents * Make/Useful.hs inst/bin/yhc src/compiler98/Package.hs src/packages/yhc-base-1.0/System/Directory.hs src/packages/haskell98-1.0/Directory.hs src/tester/Main.hs tests/conformance98/Directory/getDirContents/Main.hs best, thomas. 2007/11/25, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, On Nov 25, 2007 5:50 PM, Thomas Hartman [EMAIL PROTECTED] wrote: Thanks Dmitri, I also had to fix an issue with System.FilePath, there's a message about this on haskell cafe. In fact, takeDirectory is the right replacement for getDirectory in older FilePath. I have pushed this change too. Thanks. -- Dimitry Golubovsky Anywhere on the Web -- Dimitry Golubovsky Anywhere on the Web ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: getDirectoryContents still causing problems Re: problems building ycr2js (hopefully fixed)
Based on my experience, I wouldn't recommend doing scons fullclean; rather, I would darcs checkout and go from scratch. Annoying, but seems to work better. thomas. 2007/11/26, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, This happens sometimes as Yhc depends on many other packages not very well in sync (e. g. FilePath). Plus, internal dependencies are not always tracked very well. Or binary core format gets upgraded (that means, the core linker does not accept older versions of core files, and all of them have to be regenerated). You may see sometimes recommendations in the Yhc mailing list: pull patches, then do scons fullclean. Or re-check the whole repo out, which is basically the same. Thanks. On 11/26/07, Thomas Hartman [EMAIL PROTECTED] wrote: False alarm. I rm -rf ed yhhc, fresh darcs got the latest yhc, reinstalled yhc, and redid (cd src/translator/js; make all install) and it built. 2007/11/26, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, It looks like this comes from Yhc, not from the Javascript backend. Have you done the full sequence of (starting with clean repo)? darcs get darcs.haskell.org/yhc scons core=1 build scons prefix=... install # whatever your stuff goes, and yhc will be in bin/ from that, and this bin/ should be on your path (cd src/translator/js; make all install) Please let me know where it fails. Thank you. On 11/26/07, Thomas Hartman [EMAIL PROTECTED] wrote: still having problems darcs pulling your updates, related to System.FilePath. did you make clean and then make again? I darcs pulled everything. (cd src/translator/js; make all install) ... ... (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskell; \ for f in `find . -name '*.hs' | sort` ; do make -s -f /home/thartman/haskell-installs/yhc-install/yhc/src/translat\ or/js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) -s flag silences, we don't want that, with verbose output again we see that make is failing for a huge number of packages (cd /home/thartman/haskell-installs/yhc-install/yhc/src/translator/js/lib/h\ askell; \ for f in `find . -name '*.hs' | sort` ; do make -f /home/thartman/haskell-installs/yhc-install/yhc/src/translator/\ js/Makefile `dirname $f`/`basename $f .hs`.ycr ; done) yhc --core --no-bytecode CDOM/Level1/DomUtils.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) make: *** [CDOM/Level1/DomUtils.ycr] Error 1 yhc --core --no-bytecode CDOM/Level1/Events.hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) ... [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhc/src/translator/js/lib/haskellyhc --core --no-bytecode CDOM/Level1/DomUtils\ .hs yhc: /home/thartman/haskell-installs/yhc-install/yhc/inst/lib/yhc/packages: getDirectoryContents: does not exist (No such fi\ le or directory) Unfamiliar with yhc, I couldn't figure out where getDirectory contents is being called from. Grepping at the root, I guess something here is causing problems [EMAIL PROTECTED]:~/haskell-installs/yhc-install/yhcgrep -irl getDirectoryContents * Make/Useful.hs inst/bin/yhc src/compiler98/Package.hs src/packages/yhc-base-1.0/System/Directory.hs src/packages/haskell98-1.0/Directory.hs src/tester/Main.hs tests/conformance98/Directory/getDirContents/Main.hs best, thomas. 2007/11/25, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, On Nov 25, 2007 5:50 PM, Thomas Hartman [EMAIL PROTECTED] wrote: Thanks Dmitri, I also had to fix an issue with System.FilePath, there's a message about this on haskell cafe. In fact, takeDirectory is the right replacement for getDirectory in older FilePath. I have pushed this change too. Thanks. -- Dimitry Golubovsky Anywhere on the Web -- Dimitry Golubovsky Anywhere on the Web -- Dimitry Golubovsky Anywhere on the Web ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: New slogan for haskell.org
Henning Thielemann wrote: Now my idea was, that making links to glossary articles leaves the slogan as short as it is, and allows people to find out quickly about the words they still don't know. An explanation why Haskell's features are useful for programmers is still required. +1 But we'd probably need the glossary articles first before linking to them :) Regards, apfelmus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New demo/test program for Yhc Javascript backend
2007/11/26, Dimitry Golubovsky [EMAIL PROTECTED]: Thomas, All published examples (source, html) go into web/jsdemos subdirectory (from the root of the Yhc repo source tree). right; it would be nice to have a makefile (or makefiles) there that works out of the box, rather than relying on the wiki http://haskell.org/haskellwiki/Yhc/Javascript/Users_guide#Building_and_installation_on_Unix which, among other things, requires cleaning up tabs for the formatting to work. Even if it can't be incorporated into the buildbot, it would be nice to have some working make examples to orient one's self. Secondly, with regards to your cps changes, are you aware of *any* demos that will compile from head? I want to get going with this because I have a situation where ycr2js would be really useful for an in-house project, client side table filtering on large tables. Maybe I should say a bit about this as well so you can tell me if this seems realistic, I'll write a separate email about that. t. Not all of them may be compilable at the moment though (and some will never be compilable in the future, just kept there for historic reasons - that's why they are not being tested by the buildbot). I am currently going through transition from plain CPS to Cont monad, so regular monadic notation can be used instead of CPS. However I am experiencing memory leaks in MSIE (try the EchoM example) which I did not expect to happen (never had them in plain CPS). If I cannot fix that I'll roll back to plain CPS. On 11/26/07, Thomas Hartman [EMAIL PROTECTED] wrote: It would be really helpful if you could include this (and other) examples in an /examples directory under src/translator/js -- Dimitry Golubovsky Anywhere on the Web ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: New slogan for haskell.org
apfelmus wrote: But we'd probably need the glossary articles first before linking to them :) +12 I added added alpha, beta and eta conversion a while back. (And then some kind soul corrected it because half of what I wrote was actually *wrong*...) Anybody want to take a stab at all 15 kinds of morphisms? :-} ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: New slogan for haskell.org
On Mon, 26 Nov 2007, Andrew Coppin wrote: apfelmus wrote: But we'd probably need the glossary articles first before linking to them :) +12 I added added alpha, beta and eta conversion a while back. (And then some kind soul corrected it because half of what I wrote was actually *wrong*...) Anybody want to take a stab at all 15 kinds of morphisms? :-} Let's start with polymorphism. :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New slogan for haskell.org
On 26 Nov 2007, at 15:50, Henning Thielemann wrote: On Mon, 26 Nov 2007, Thomas Davie wrote: On 26 Nov 2007, at 15:15, Henning Thielemann wrote: On Thu, 4 Oct 2007, Don Stewart wrote: The Haskell website has the rather strange motivational text: Haskell is a general purpose, purely functional programming language featuring static typing, higher order functions, polymorphism, type classes, and monadic effects. Haskell compilers are freely available for almost any computer. To continue an old thread: What about turning the strange words like 'monadic effects' into links to glossary articles? Btw. where is 'lazy' ? I believe the point of this discussion was that anyone reading the Haskell webpage will currently get about as far as featuring static typing, and go this is all very nice, but what exactly does this language do for me? Why should I use it?. Take for example what the python website says: I didn't want to repeat the discussion. I think the discussion ended with: Anything more helpful would be too long for the title line at haskell.org, and a more detailed explanation (but not a generic advertisement like that from Python) should be reachable easily. Now my idea was, that making links to glossary articles leaves the slogan as short as it is, and allows people to find out quickly about the words they still don't know. An explanation why Haskell's features are useful for programmers is still required. But the point is that this section of the site is the bit that's meant to be an advertisement -- we're trying to encourage people to read more, and quite frankly, making it a fist full of links would make at least me think Well bugger this if I have to read 10 pages before I even have a clue what it is. Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] idea for ycr2js demo, actually meant for an in-house project. is this realistic?
As I mentioned in a previous post, I've been spending quite some time trying to get live with ycr2js because there's a project it would be useful for for my day job, as well as making another nice demo to add to the list. Basically, I have some functionality that does client-side filtering of large html tables. It's pretty smart -- it can filter on multiple columns, and the filter can be any javascript expression from String - Bool (to use haskell terminology in a javascript context). The filter works by hiding rows that don't match the filter; it's built on mochikit. Unfortunately this is rather ugly from the user's perspective. You have to type something like x.match(my string) into the search string or (x 5 x 7) where x is some variable buried in the javascript. I would like for the user to be able to enter search criteria in a more intuitive google style =skittles or (=~mr. goodbar and =~15 grams) so you need a parser that takes the search criteria and converts it into a function from (String - Bool) This parser is relatively easy to build in haskell; I built it. It's surely also doable in javascript, but not as nicely, easily, and cleanly, and being a better haskell than javascript programmer as well, I would rather generate the javascript from haskell. So at any rate what I have is -- parser from String - (String - Bool) (haskell) -- working html/javascript built on mochikit that filters a multicolumn table with multiple filter expressions. There is a function here that takes a string and returns a bool, but it's icky, doesn't recognize quoted strings, doesn't recognize boolean and/or or parentheses. I want to replace it with a function generated from haskell that does all of these things. What I need is to combine these two components. I'll try and post some minimal source code for the parser and the javascript/mochikit stuff soon, and if this problem is tractable it can become another example for ycr2js. A possible reason why this wouldn't work is that when you're using the ycr2js stuff, *everything* has to be generated; it doesn't play well plugging in an existing javascript function with a generated one. I'd be surprised if that was the case, but since I haven't actually successfully generated any code yet i guess anything possible. At any rate, if this sort of thing could cause issues please someone in the know give me fair warning. thomas. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] return in Monad class necessary?
I wonder whether it is a typical mistake of beginners to write 'return' within a do-block (that is, not at the end) and if it is possible to avoid this mistake by clever typing. In a proper monad 'return' can be fused with subsequent actions, and thus it is not necessary within a sequence of actions. However, although sensible, 'return' is also not required at the end of a block. Has someone already thought about a replacement for monads? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Libraries need a new owner
Hello Folks, Adrian Hey wrote: If anyone is interested in the job then I suggest they contact myself or Jean-Philippe Bernardy. Sigh..no sooner than I go and write something like that than the IEE (or I should say IET) go and break my mail alias. So sorry if anyone did actually try to contact me and got a their mail bounced. It should be working again now. Regards -- Adrian Hey ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New demo/test program for Yhc Javascript backend
Fair enough, I can wait for a couple of days.
You might want to fix
[EMAIL
PROTECTED]:~/haskell-installs/yhc-install/yhc/src/translator/js/testdarcs
whatsnew
{
hunk ./src/translator/js/test/Makefile 12
- $(YHC) -includes ../lib/haskell -linkcore $
+ $(YHC) --includes ../lib/haskell --linkcore $
}
immediately though.
This is the only makefile for the javascript stuff in the repo, and it
doesn't work because of - instead of --. Given your darcs log message
that the javascript compiler would be broken I initially assumed that
was the reason and not a flags change.
More questions. So okay, it builds, I have Test1.html. It's a blank
file with a bunch of javascript. I have firebug, so I can ask execute
stuff in the javascript console. But I can't figure out what to
execute. factorial isn't there, nor sumlst... none of the interesting
looking functions? So what is this supposed to do? And can I change
the makefile so that at least it generates javascript where I can
execute the interesting functions in the firebug console?
thomas.
2007/11/26, Dimitry Golubovsky [EMAIL PROTECTED]:
Thomas,
OK, let's try to get on the same page regarding where the project is.
The Javascript generator is maybe not optimal, but it works.
DOM bindings are generated from W3C's IDL files, so everything DOM
provides may be used by Haskell programs, whether in CPS notation, or
monadic, this will become clear, which form to use, in the near
future.
The recent HsWTKDemo works well in major browsers (FF, MSIE, Opera)
except for Safari, but this is probably a hard case due to the lack of
debugging information.
If you look at its source
http://darcs.haskell.org/yhc/web/jsdemos/HsWTKDemo.hs
(no, you cannot compile it at the moment because it is plain CPS) you
may see some stuff related to static page layout definition in
declarative way (look for upcntW, factW, etc.) This part is almost
finalized wrt notation. What's left undecided is whether to use plain
CPS notation, or monadic notation for parts of the code that involve
imperative stuff (see e. g. updateD function where node's children are
replaced in order to update what's displayed).
This all works perfectly in plain CPS. Understanding that nowadays
Monads are mainstream, I am trying to adopt monadic notation based on
the Cont monad instead of plain CPS. I ran one example (EchoM) on MSIE
and noticed memory leaks on each user's action. However when the page
is unloaded, MSIE shrinks in size which is a good sign. I think I know
where the cause is, tonight I'll try to fix it. If unsuccessful, I'll
probably unroll all monadic changes.
Next steps are:
1. Finalize the code notation for static layout and imperative part
and check the base library into the Yhc repo
2. Generate haddock documentation
3. Write a better documentation for developers
4. Set up a web service that would allow everybody to submit their
Haskell source and generate HTML page with Javascript in response;
this I think can be done based on the hpaste program (backed by
Happs).
Just for now, you have to wait a couple days while I am straightening
the monadic thing out. I'd appreciate if you look at the code of
HsWTKDemo and give me your impressions about notation, etc.
Thank you.
--
Dimitry Golubovsky
Anywhere on the Web
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Re: [Haskell-cafe] New slogan for haskell.org
On Thu, 2007-10-04 at 10:36 -0700, Don Stewart wrote: It was raised at CUFP today that while Python has: Python is a dynamic object-oriented programming language that can be used for many kinds of software development. It offers strong support for integration with other languages and tools, comes with extensive standard libraries, and can be learned in a few days. Many Python programmers report substantial productivity gains and feel the language encourages the development of higher quality, more maintainable code. With the links from the start about using Python for various purposes, along with reassuring text about licenses and so on. Note its all about how it can help you. The Haskell website has the rather strange motivational text: Haskell is a general purpose, purely functional programming language featuring static typing, higher order functions, polymorphism, type classes, and monadic effects. Haskell compilers are freely available for almost any computer. Which doesn't say why these help you. Any suggestions on a 2 or 3 sentence spiel about what's available? Here's some quick points: General purpose: applications from OS kernels to compilers to web dev to ... Strong integration with other languages: FFI, and FFI binding tools Many developer tools: debugger, profiler, code coverage, QuickCheck Extensive libraries: central library repository, central repo hosting Productivity, robustness, maintainability: purity, type system, etc Parallelism! Haskell is a general-purpose, pure functional programming languages that puts many interesting results from research into a practical programming language. It's features include: * Static typing with type inference: enables writing robust and fast programs quickly and makes large code bases maintainable. * Higher-order functions, polymorphism, and laziness: enables higher levels of abstraction, more composable, thus reusable code. * Purity: helps keeping your code maintainable and testable. Haskell comes with many libraries, freely available compilers for almost any computer, debuggers, profilers, code coverage and testing tools. That seems short enough to me. Things that could find their way in are: monads: for the embedded DSL angle paralellism: mention STM and high-level combinators ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] return in Monad class necessary?
Hello Henning, Monday, November 26, 2007, 9:48:29 PM, you wrote: I wonder whether it is a typical mistake of beginners to write 'return' within a do-block (that is, not at the end) don't forget that `return` is also used to force evaluation: do let n = a+b return $! n writeChan c (n,1) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New slogan for haskell.org
Thomas Davie wrote: But the point is that this section of the site is the bit that's meant to be an advertisement -- we're trying to encourage people to read more, and quite frankly, making it a fist full of links would make at least me think Well bugger this if I have to read 10 pages before I even have a clue what it is. Mmm, the man has a point... I guess it's kinda hard to explain in just a few words why Haskell is actually so damn cool. I mean, you can write it enables you to write less code. (Ever heard that one before?) Or you could say it makes your programs more reliable (er, yes, I believe we've heard that all before too). Or even, it enables you to easily harness multicore computing (except that it isn't true - yet). Hmm... so we seem to have a choice between verbose statements that nobody is going to read, or hopeful promises of better which we can't substansiate. Oh dear... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Pretty-printing peg solitaire boards
Actually, I did mean to start with: (...) #0# #0# ### ### ### ### ### (...) Heh. He's in for a surprise, there are actually solutions for this. (...) If you don't want to spoil it here, and it won't take too much of your time to write it down, you can send it to my e-mail: '[EMAIL PROTECTED]' (...) I'll try to find that book, we'll like to read it. It's a series of three books actually. Sadly it's been a long time since I've read them so I forgot which volume covers which topics. Actually, it seems there's an old edition in two volumes and a new one, in four volumes. I just read the first chapter of volume I in Amazon, and it's really a nice reading. Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Building MissingH on Windows
Hi, I'm trying to build MissingH (0.18.6) on Windows, but it looks like (probably because of changes in Cabal) the Setup.hs is broken. Im using GHC 6.8.1. Following message: $ runhaskell Setup.hs configure Setup.hs:19:35: Couldn't match expected type `(Either GenericPackageDescription PackageDescription, HookedBuildInfo)' against inferred type `PackageDescription' In the first argument of `(confHook defaultUserHooks)', namely `mydescrip' In the expression: let mydescrip = case os of mingw32 - ... _ - ... in (confHook defaultUserHooks) mydescrip flags In the definition of `customConfHook': customConfHook descrip flags = let mydescrip = ... in (confHook defaultUserHooks) mydescrip flags I'm new to Cabal and I couldn't see a fast way to fix it. Thanks, Nicu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Building MissingH on Windows
On Mon, 2007-11-26 at 21:24 +0100, [EMAIL PROTECTED] wrote: Hi, I'm trying to build MissingH (0.18.6) on Windows, but it looks like (probably because of changes in Cabal) the Setup.hs is broken. Im using GHC 6.8.1. Following message: $ runhaskell Setup.hs configure Setup.hs:19:35: Couldn't match expected type `(Either GenericPackageDescription PackageDescription, HookedBuildInfo)' against inferred type `PackageDescription' In the first argument of `(confHook defaultUserHooks)', namely `mydescrip' In the expression: let mydescrip = case os of mingw32 - ... _ - ... in (confHook defaultUserHooks) mydescrip flags In the definition of `customConfHook': customConfHook descrip flags = let mydescrip = ... in (confHook defaultUserHooks) mydescrip flags I'm new to Cabal and I couldn't see a fast way to fix it. Thanks, Nicu Try replacing the original files with the attached files. -- arch-tag: MissingH main description file Name: MissingH Version: 0.18.6 Cabal-Version: = 1.2 License: GPL Maintainer: John Goerzen [EMAIL PROTECTED] Author: John Goerzen Copyright: Copyright (c) 2004-2007 John Goerzen license-file: COPYRIGHT extra-source-files: COPYING homepage: http://software.complete.org/missingh Category: Unclassified synopsis: Large utility library Description: MissingH is a library of all sorts of utility functions for Haskell programmers. It is written in pure Haskell and thus should be extremely portable and easy to use. Stability: Beta Library Hs-Source-Dirs: src Exposed-Modules: Data.String, System.IO.Utils, System.IO.Binary, Data.List.Utils, System.Daemon, Text.ParserCombinators.Parsec.Utils, Test.HUnit.Utils, Network.Email.Mailbox, Control.Concurrent.Thread.Utils, Network.Email.Sendmail, Data.CSV, System.Cmd.Utils, Data.Progress.Tracker, Data.Progress.Meter, Data.Quantity, Data.Map.Utils, System.Path, System.Path.NameManip, System.Path.WildMatch, System.Path.Glob, System.Time.Utils, System.Time.ParseDate, Network.Utils, Network.SocketServer, Data.Either.Utils, Data.Maybe.Utils, Data.Bits.Utils, Data.Hash.CRC32.Posix, Data.Hash.CRC32.GZip, Data.Hash.MD5, Data.Hash.MD5.Zord64_HARD, Data.Compression.Inflate, System.FileArchive.GZip, System.IO.HVFS, System.IO.HVFS.Combinators, System.IO.HVFS.InstanceHelpers, System.IO.HVFS.Utils, System.IO.HVIO, System.IO.StatCompat, System.IO.WindowsCompat, System.IO.PlafCompat, System.Posix.Consts, System.Debian, System.Debian.ControlParser, Data.MIME.Types, System.Console.GetOpt.Utils Extensions: ExistentialQuantification, OverlappingInstances, UndecidableInstances, CPP Build-Depends: network, parsec, base, haskell98, mtl, HUnit, regex-compat, QuickCheck, filepath, hslogger if !os(windows) Build-Depends: unix GHC-Options: -O2 Executable runtests Buildable: False Main-Is: runtests.hs HS-Source-Dirs: testsrc, . Extensions: ExistentialQuantification, OverlappingInstances, UndecidableInstances, CPP #!/usr/bin/env runhaskell module Main where import Distribution.Simple main :: IO () main = defaultMain ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Building MissingH on Windows
See also: http://haskell.org/haskellwiki/Upgrading_packages You probably have to adjust the build-depends field, due to the base split up. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problems with split-objs
I've followed the instructions at [1] to create a .deb of vty[2]. It seems the helper scripts for Debian passes `--enable-split-obj' when running `./Setup.lhs configure'. This results in numerous multiple definitions of stuff. I have a few questions regarding this... I think I understand what --split-objs does, but why doesn't it work for vty? I've debianised other haskell libs using the same method without problems. The only difference I can see is that vty uses FFI. Is that what causes the problems? How do I fix this? I'd rather not go in and manually change any automatically generated files, and the file that passes `--enable-split-objs' is automatically generated :( /M [1]: http://haskell.org/haskellwiki/Creating_Debian_packages_from_Cabal_package [2]: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/vty-3.0.0 -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] return in Monad class necessary?
On 26 nov 2007, at 19:48, Henning Thielemann wrote: I wonder whether it is a typical mistake of beginners to write 'return' within a do-block (that is, not at the end) and if it is possible to avoid this mistake by clever typing. In a proper monad 'return' can be fused with subsequent actions, and thus it is not necessary within a sequence of actions. However, although sensible, 'return' is also not required at the end of a block. Has someone already thought about a replacement for monads? I also made that mistake in the beginning, I used return instead of lets. I don't think it's a big problem, most users will find out once they've got some more experience, and it doesn't really do any harm. -chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Announce: strict-concurrency
While writing some multi-core concurrent code I needed more precise control over which thread evaluated particular expressions. The default concurrent types, MVar and Chan, are lazy, and sometimes not suitable. The little package, http://hackage.haskell.org/cgi-bin/hackage-scripts/package/strict-concurrency Provies the MVar type, but with strict putMVar by default, and an element-strict Chan type. For some applications, these stricter types can yield improved time and space use. (For others, they can make things worse) The strict channel type in particular seems useful, as it can be used to force worker threads to evaluate to WHNF before returning values to a driver thread. Enjoy, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Browser action and new http library
I am trying to use the HTTP library 3001 for ghc 6.8 and cant figure out how to use a proxy to do a GET request as I am behind a proxy server. My thinking is that I could use the setProxy method it looks like it returns a BrowserAction? What do I do with that. Here is the current code (I havent really used the setProxy yet). -- -- HTTP LIBRARY version: HTTP-3001.0.2 import Data.Char (intToDigit) import Network.HTTP import Network.URI import Network.Browser (defaultGETRequest) import System.Environment (getArgs) import System.Exit (exitFailure) import System.IO (hPutStrLn, stderr) main = do args - getArgs case args of [addr] - case parseURI addr of Nothing - err Could not parse URI Just uri - do cont - get uri putStr cont _ - err Usage: lman url err :: String - IO a err msg = do hPutStrLn stderr msg exitFailure get :: URI - IO String get uri = do eresp - simpleHTTP (defaultGETRequest uri) resp - handleErr (err . show) eresp case rspCode resp of (2,0,0) - return (rspBody resp) _ - err (httpError resp) where showRspCode (a,b,c) = map intToDigit [a,b,c] httpError resp = showRspCode (rspCode resp) ++ ++ rspReason resp -- -- Handle Connection Errors handleErr :: Monad m = (ConnError - m a) - Either ConnError a - m a handleErr h (Left e) = h e handleErr _ (Right v) = return v -- End of File -- Berlin Brown [berlin dot brown at gmail dot com] http://botspiritcompany.com/botlist/? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Strings and utf-8
Hi, Are 'String's in GHC 6.6.1 UTF-8? Thanks, Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] return in Monad class necessary?
On Tue, 2007-11-27 at 00:15 +0100, Chris Eidhof wrote: On 26 nov 2007, at 19:48, Henning Thielemann wrote: I wonder whether it is a typical mistake of beginners to write 'return' within a do-block (that is, not at the end) and if it is possible to avoid this mistake by clever typing. In a proper monad 'return' can be fused with subsequent actions, and thus it is not necessary within a sequence of actions. However, although sensible, 'return' is also not required at the end of a block. Has someone already thought about a replacement for monads? I also made that mistake in the beginning, I used return instead of lets. I don't think it's a big problem, most users will find out once they've got some more experience, and it doesn't really do any harm. I may be mistaken, but I'm pretty sure he's talking about something different. Basically, where 'return' is confused for C's return. I have seen this occasionally in #haskell or on the mailinglist, but it doesn't seem to be a big issue. It doesn't come up all that often and it's usually quickly resolved. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Strings and utf-8
On Nov 26, 2007, at 19:23 , Maurí cio wrote: Are 'String's in GHC 6.6.1 UTF-8? No. type String = [Char] and Char stores Unicode codepoints. However, the IO system truncates them to 8 bits. I think there are UTF8 marshaling libraries on hackage these days, though. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] return in Monad class necessary?
Hi Henning,
I wonder whether it is a typical mistake of beginners
to write 'return' within a do-block (that is, not at the end)
and if it is possible to avoid this mistake by clever typing.
There are legitimate uses of return inside a do, see:
http://www.cs.york.ac.uk/fp/darcs/catch/catch_1/Analyse/Fix.hs
The code has a bit like:
x - return $ apply x addReq (\y - y{requiredBy =
Set.insert k (requiredBy y)})
x - return $ apply x delReq (\y - y{requiredBy =
Set.delete k (requiredBy y)})
i.e. modify x, which you can't do with let's because of the scoping
(they are really let-rec's). I often use return to do binding and name
shadowing in do blocks.
Having said that, when I was learning Haskell, I didn't know you could
put let in a do block, and did use the return for all variables!
Thanks
Neil
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Re: [Haskell-cafe] Strings and utf-8
allbery: On Nov 26, 2007, at 19:23 , Maurí cio wrote: Are 'String's in GHC 6.6.1 UTF-8? No. type String = [Char] and Char stores Unicode codepoints. However, the IO system truncates them to 8 bits. I think there are UTF8 marshaling libraries on hackage these days, though. Yep, utf8string, in particular. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Why aren't Float and Double Bounded?
Among numeric types, it seems that only integer types are Bounded. -- _jsn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 6.8.1 bug?
Ian Lynagh wrote: Can any of you give us a testcase for this, please? Thanks Ian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe I started to work on this but so far it's been hard to shrink the size of the test case. It seems to need a little workout before it's starts to exhibit the behavior. Also there are always time limitations. I'll keep hacking away at it. -- View this message in context: http://www.nabble.com/ghc-6.8.1-bug--tf4810375.html#a13964202 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A tale of three shootout entries
In some spare time over the holidays I cooked up three shootout entries, for Fasta, the Meteor Contest, and Reverse Complement. I should probably have tossed them to haskell-cafe before submission, for review and ideas, but they're up now. In any case, all three were great learning experiences, but could use some other eyes and ideas to be the best that they can. First up is the meteor-contest entry. http://shootout.alioth.debian.org/gp4/benchmark.php? test=meteorlang=ghcid=5 This is the clear win of the bunch, with significantly improved time thanks to its translation of the better algorithm from Clean. However, it's still missing something. Nearly all its time is spent in a tight loop in the solveCell function near the end of the code. I tried unboxing this, but failed because it spends the bulk of its time applying a bitwise and between the recursively passed value and a piece of data retrieved from the masksAtCell data structure which is of type :: Array (Row,Col) (Array Color [Mask]). (Note that Mask, Color, Row and Col are all type synonyms for Int that I added for readability). As each Mask is stored in this list, the masks can't easily be unboxed -- some sort of custom data structure built using the FFI seems in order here. If anyone wants to tackle this, I think it could be a big win for performance. Next is reverse-complement. http://shootout.alioth.debian.org/gp4/benchmark.php? test=revcomplang=ghcid=3 This *would* be a big win except I dimly doubled memory usage from the previous entry due to filtering newlines explicitly -- which does, one should note, provide a large performance gain. The solution here seems the most obvious -- roll the newline stripping into the destructive modifications performed in the revcomp function, as the winning C++ entry does. I'll probably get around to this eventually, but if someone else wants to try to implement this or any other performance improvements, please jump right in. Additionally, there might be some other tricks to reducing its memory usage that escape me at the moment (noting, of course, that using a strict bytestring, as we should, its unavoidable that we consume the entire contents of the input at once... I think?) Finally, there's fasta. http://shootout.alioth.debian.org/gp4/benchmark.php? test=fastalang=ghcid=2 This one really depresses me. It outperforms the previous version by roughly 20% on my machine (PPC) but underperforms by roughly the same amount on the shootout box. If you compare it to dons previous version, the optimizations I attempted should be pretty obvious. First, I precompute the partial sums for the frequency tables and alter the choose function accordingly. This is a pretty basic measure that all the better entries seem to do. Next, I unboxed the random function, which yielded big speedups However, given that we use an unfoldN, as we should, I couldn't very well pass it a function that returned something of kind #, (especially as Maybe, which unfoldN uses, is of kind *-*). Thus, I hid the unrolled loop in a lazy list of floats that is passed instead of a random seed. I suspect that for some reason I don't understand relating to differences in processors, GHC's internal handling of floating point math, or who knows what, this somehow is the source of the slowdown. If someone with an Intel Pentium 4 machine comparable to that of the shootout box wants to take a look at this code and see why it underperforms, I'd be much obliged. It really seems to me that GHC's fasta performance is far below where it should be (4x slower than Java!) , and I'd like to get its numbers up somehow. Thanks, Sterl p.s. It looks like they've depreciated chameneos in favor of a new version, chameneos-redux. As this was one of the places Haskell really rocked the competition, it would probably be worth updating the Haskell entry for the new benchmark. Also, the n-bodies benchmark seems like another that could be much improved. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A tale of three shootout entries
s.clover: In some spare time over the holidays I cooked up three shootout entries, for Fasta, the Meteor Contest, and Reverse Complement. I Yay! First up is the meteor-contest entry. http://shootout.alioth.debian.org/gp4/benchmark.php? test=meteorlang=ghcid=5 This is the clear win of the bunch, with significantly improved time thanks to its translation of the better algorithm from Clean. Well done! Though looks like we'll have to follow the C++ implementation to be really competitive. Next is reverse-complement. http://shootout.alioth.debian.org/gp4/benchmark.php? test=revcomplang=ghcid=3 Very good. I'm glad someone looked at that, since the old code was moderately naive (first bytestring effort). Finally, there's fasta. http://shootout.alioth.debian.org/gp4/benchmark.php? test=fastalang=ghcid=2 Yeah, we should do something better here. Hmm. p.s. It looks like they've depreciated chameneos in favor of a new version, chameneos-redux. As this was one of the places Haskell really rocked the competition, it would probably be worth updating Definitely. I note also we're beating Erlang on the new thread-ring benchmark too, http://shootout.alioth.debian.org/gp4/benchmark.php?test=threadringlang=all the Haskell entry for the new benchmark. Also, the n-bodies benchmark seems like another that could be much improved. Yeah, that's a hard one. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New slogan for haskell.org
On Nov 26, 2007 11:38 AM, Thomas Schilling [EMAIL PROTECTED] wrote: Haskell is a general-purpose, pure functional programming languages that puts many interesting results from research into a practical programming language. It's features include: I think it is stronger to say many powerful results rather than many interesting results. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] return in Monad class necessary?
On 26 Nov 2007, at 10:48 AM, Henning Thielemann wrote: I wonder whether it is a typical mistake of beginners to write 'return' within a do-block (that is, not at the end) and if it is possible to avoid this mistake by clever typing. In a proper monad 'return' can be fused with subsequent actions, and thus it is not necessary within a sequence of actions. However, although sensible, 'return' is also not required at the end of a block. Has someone already thought about a replacement for monads? As has been said, this isn't a big issue, and return is quite useful. Furthermore, I can think of several cases where it would be awkward (to say the least) to dispense with return, and it's an invaluable base case for inductive definitions, e.g. of liftMn (which would have to replace it, I suppose). And besides that, if there is one thing Haskellers believe more than anything else, it must surely be that every associative operator deserves a unit... jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
