February 2007 - Haskell-Cafe

LugRadio talk
by Dougal Stanton 16 Feb '07

16 Feb '07

So which one of you wonderful people volunteered to give a talk on Haskell at the coming LugRadio Live? I'm afraid I didn't catch the name, though it might have been a Magnus something? It might be enough to make me go if I knew there would be some funky Haskelling going on. Cheers, D. -- Dougal Stanton

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Newbie Q: GHCi: Where “List” module is imported from?
by Dmitri O.Kondratiev 16 Feb '07

16 Feb '07

Going through "Haskell. The Craft of Functional Programming" book , in section 16.8 I found a Set module example. Module declarations starts with: import List hiding (union) "Set" module here is built with list and uses among other things list comparison functions such as (==) and (<=). For example: eqSet :: Eq a => Set a -> Set a -> Bool eqSet (SetI xs) (SetI ys) = (xs == ys) Q1: Where "List" module is imported from? GHC "Base" package contains "Data.List" module, not just "List" module. Besides, "Data.List" does not have (<=) function. Q2: Any tutorial on using GHC libraries out there? Thanks! Dima

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How to solve this problem?It's quite easy in PHP.
by keepbal 16 Feb '07

16 Feb '07

For example, ----------------------------------- <?php //test.php require ("tiny.php");//Tiny is a small template engine. $tn=new Tiny(); $arr=new Array(); $arr['a']='1'; $arr['b']='2'; $arr['c']='3'; $tn->set('arr',$arr); $tn->show('_test.php'); ?> ----------------------------------- <?php require('_header.php');?> <?php foreach($arr as $key => $val){ echo "$key = $val <br>"; } ?> <?php require('_footer.php');?> ----------------------------------- a = 1 b = 2 c = 3 -----------------------------------

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new member
by P. R. Stanley 16 Feb '07

16 Feb '07

Hi Paul here - new member - checking to see my account is fully functional. Does the list know of another list where I can post questions on functional programming and the related mathematics? I'm assuming Haskell Cafe is mainly for discussions on Haskell programming and not so much the underlying theory. Any help would be appreciated. Cheers Paul

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Strange memory consumption problems in something that should be tail-recursive
by Jefferson Heard 16 Feb '07

16 Feb '07

Hi, I am running the following code against a 210 MB file in an attempt to determine whether I should use alex or whether, since my needs are very performance oriented, I should write a lexer of my own. I thought that everything I'd written here was tail-recursive, but after compiling this with GHC 2.4.6, and running it, I eat up 2GB of RAM in less than a second. So far, I have tried token and character oriented Parsec parsers and alex and alex is winning by a factor of 2. I would like to be able to tokenize the entirety of a 1TB collection in less than 36 hours on my current machine, which is where alex has gotten me so far. Thanks in advance! -- Jeff --- module Main where import qualified FileReader import qualified Data.Set as Set punct = foldl (flip Set.insert) Set.empty "<,>.?/:;\"'{[}]|\\_-+=) (*&^%$##@!~`" stripTagOrComment [] = [] stripTagOrComment ('>':rest) = rest stripTagOrCOmment (c:rest) = stripTagOrComment rest pass1 :: String -> String -> String pass1 left [] = left pass1 left ('<':right) = pass1 left (stripTagOrComment right) pass1 left (' ':right) = pass1 left right pass1 left (c:right) | Set.member c punct = pass1 (' ':c:' ':left) right | otherwise = pass1 (c:left) right pass2 :: [String] -> String -> Char -> String -> [String] pass2 left word ' ' [] = word:left pass2 left word c [] = (c:word):left pass2 left word ' ' (' ':right) = pass2 left word ' ' right pass2 left word ' ' (c:right) = pass2 (word:left) "" c right pass2 left word l (c:right) = pass2 left (l:word) c right tokenize = (pass2 [] "" ' ') . (pass1 []) main = do file <- do FileReader.trecReadFile "trecfile" print (tokenize (head (tail file))) -- print (length (map (runParser tokenizeDoc [] "") file))

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State of OOP in Haskell
by Alexy Khrabrov 16 Feb '07

16 Feb '07

...In the tradition of the "letters of an ignorant newbie"... What's the consensus on the OOP in Haskell *now*? There're some libraries such as OOHaskell, O'Haskell, and Haskell~98's own qualified type system with inheritance. If I have GHC, which way to do anything OOP-like is considered "right" today? Cheers, Alexy

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SoC: Port Haddock to use GHC
by Nicolas Frisby 16 Feb '07

16 Feb '07

I am very ready for a Haddock that can swallow infix typenames. In dons's recent overview of the last SoC, a darcs repo for Waern's project was listed. I jumped at the link but couldn't find much documentation (i.e. the README file is GHC's, not the SoC project's). Some Google queries followed with no success. My questions for Waern or anyone else who knows where to look: 1) Where to look for more complete documentation? 2) Is the implementation integrated into GHC yet? GHC head? Separate repo? 3) What Haddock features are supported as of yet? 4) Is it still actively developed? Thanks for any hints, Nick

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Lisp on xkcd.com, very funny!
by Magnus Therning 16 Feb '07

16 Feb '07

I think the readers of this list will appreciate this http://xkcd.com/comics/lisp.jpg /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus(a)therning.org Jabber: magnus.therning(a)gmail.com http://therning.org/magnus Software is not manufactured, it is something you write and publish. Keep Europe free from software patents, we do not want censorship by patent law on written works. What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman

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Summer of code and spam
by Magnus Therning 16 Feb '07

16 Feb '07

There seems to be a serious problem with spam on Haskell's SoC page: http://tinyurl.com/fl2dw Or maybe that's a general problem for hackage? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus(a)therning.org Jabber: magnus.therning(a)gmail.com http://therning.org/magnus

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Unicode Strings and ICU for Haskell
by Brian Smith 16 Feb '07

16 Feb '07

Has anybody written a wrapper for ICU (International Components for Unicode) for Haskell (GHC and/or Hugs)? I am processing Thai text and I want to use the ICU word-breaking, collation, encoding conversion, and transliteration services from my Parsec-based parsers. Also, what is the plan for Unicode string processing for Haskell? What is the standard module for high-performance, Unicode-capable strings? Thanks, Brian [1] http://icu.sourceforge.net/ [2] http://www-306.ibm.com/software/globalization/icu/index.jsp

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