Comments on: A Haskell regular expression tutorial http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/ Bryan O'Sullivan's blog Wed, 08 Feb 2012 06:41:38 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: replacement / substition with Haskell regex libraries http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-328950 replacement / substition with Haskell regex libraries Tue, 31 Jan 2012 10:54:17 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-328950 [...] p.s. Haskell documentation for this is pretty lacking. Some low-level API notes are here: http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/ [...] [...] p.s. Haskell documentation for this is pretty lacking. Some low-level API notes are here: http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/ [...]

]]> By: missingfaktor http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-328318 missingfaktor Fri, 30 Dec 2011 06:44:31 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-328318 Doesn't work for me. haskell>("22" =~ "*") :: Bool :1:7: No instances for (RegexMaker Regex CompOption ExecOption [Char], RegexContext Regex [Char] Bool) arising from a use of `=~' Possible fix: add instance declarations for (RegexMaker Regex CompOption ExecOption [Char], RegexContext Regex [Char] Bool) In the expression: ("22" =~ "*") :: Bool In an equation for `it': it = ("22" =~ "*") :: Bool Doesn’t work for me.

haskell>(“22″ =~ “*”) :: Bool

:1:7:
No instances for (RegexMaker Regex CompOption ExecOption [Char],
RegexContext Regex [Char] Bool)
arising from a use of `=~’
Possible fix:
add instance declarations for
(RegexMaker Regex CompOption ExecOption [Char],
RegexContext Regex [Char] Bool)
In the expression: (“22″ =~ “*”) :: Bool
In an equation for `it’: it = (“22″ =~ “*”) :: Bool

]]> By: czhedu http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-326837 czhedu Sat, 15 Oct 2011 16:05:43 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-326837 "In practice, you will want to avoid the Text.Regex.Posix implementation; it’s terribly slow, and too strict besides." ---- Then the question is: what shall we use??? According to the comparision on http://www.haskell.org/haskellwiki/Regular_expressions#Overview http://www.haskell.org/haskellwiki/Regular_expressions#Sample_benchmark I recommend regex-tdfa, which is very fast and also native implementation in haskell. http://hackage.haskell.org/package/regex-tdfa “In practice, you will want to avoid the Text.Regex.Posix implementation; it’s terribly slow, and too strict besides.” —- Then the question is: what shall we use???

According to the comparision on
http://www.haskell.org/haskellwiki/Regular_expressions#Overview
http://www.haskell.org/haskellwiki/Regular_expressions#Sample_benchmark

I recommend regex-tdfa, which is very fast and also native implementation in haskell.
http://hackage.haskell.org/package/regex-tdfa

]]> By: czhedu http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-326836 czhedu Sat, 15 Oct 2011 15:59:48 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-326836 OK. I figure out how to do the above in latest GHC 7. Just use “foo foo foo” =~ “foo” :: [[String]] What is [[String]] ??? Yes, its the List of String List. Then you can use head/tail etc to get subgroup of matches. This is extremely useful, when you want to use captured parenthesized subexpressions. OK. I figure out how to do the above in latest GHC 7. Just use

“foo foo foo” =~ “foo” :: [[String]]

What is [[String]] ??? Yes, its the List of String List. Then you can use head/tail etc to get subgroup of matches. This is extremely useful, when you want to use captured parenthesized subexpressions.

]]> By: czhedu http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-326834 czhedu Sat, 15 Oct 2011 15:45:16 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-326834 "foo foo foo" =~ "foo" :: [String] is really awesome. However it doesn't work any more in GHC 7.0.3. “foo foo foo” =~ “foo” :: [String] is really awesome. However it doesn’t work any more in GHC 7.0.3.

]]> By: Haskell - Return type overloading in Haskell - Matthew Manela - Farblondzshet in Code http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-305846 Haskell - Return type overloading in Haskell - Matthew Manela - Farblondzshet in Code Fri, 17 Jun 2011 19:00:35 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-305846 [...] module.  This module contains regular expression functions and in particular exposes the =~ operator. This operator lets you match a regex pattern against a string and its behavior is overloaded based [...] [...] module.  This module contains regular expression functions and in particular exposes the =~ operator. This operator lets you match a regex pattern against a string and its behavior is overloaded based [...]

]]> By: Bastien http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-267924 Bastien Tue, 31 Aug 2010 23:58:18 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-267924 => Peter, use [[:digit:]] instead of [:digit:]. Common pitfall. Think about what you would have to write if you would enclose two or more character classes in the same range. => Peter,
use [[:digit:]] instead of [:digit:]. Common pitfall. Think about what you would have to write if you would enclose two or more character classes in the same range.

]]> By: Peter White http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-244105 Peter White Fri, 28 Aug 2009 18:57:58 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-244105 Oh I forgot to say that the tutorial was very useful! Oh I forgot to say that the tutorial was very useful!

]]> By: Peter White http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-244104 Peter White Fri, 28 Aug 2009 18:54:27 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-244104 I am unable to get the regular expression matching to work when I use Posix character classes such as [:digit:]. For example, if I use "^[:digit:] +INTRODUCTION", this does not match the string "1 INTRODUCTION", but if I use what is supposed to be equivalent, namely "^[0-9] +INTRODUCTION", this does match the string "1 INTRODUCTION". Any ideas what I am doing wrong? I am unable to get the regular expression matching to work when I use Posix character classes such as [:digit:]. For example, if I use “^[:digit:] +INTRODUCTION”, this does not match the string “1 INTRODUCTION”, but if I use what is supposed to be equivalent, namely “^[0-9] +INTRODUCTION”, this does match the string “1 INTRODUCTION”. Any ideas what I am doing wrong?

]]> By: Haskell Problem: Unix grep « Clark Grubb’s Blog http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/comment-page-1/#comment-231296 Haskell Problem: Unix grep « Clark Grubb’s Blog Mon, 25 May 2009 06:54:07 +0000 http://www.serpentine.com/blog/2007/02/27/a-haskell-regular-expression-tutorial/#comment-231296 [...] searches, the -l and -L flags, and regular expressions. Regular expressions were difficult. This blog post explains how to use Test.Regex.Posix, but I had difficulty compiling the code. Instead [...] [...] searches, the -l and -L flags, and regular expressions. Regular expressions were difficult. This blog post explains how to use Test.Regex.Posix, but I had difficulty compiling the code. Instead [...]

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