Re: [Haskell-cafe] multi-line regex

Multi-line regular expressions are indeed powerful. Rob Pike has a good paper on it available at: http://doc.cat-v.org/bell_labs/structural_regexps/se.pdfhttp://code.google.com/p/sregex/ http://code.google.com/p/sregex/Explains how line-based regular expressions are limiting etc. The Sam and Acme editors supported these. Python does too now. http://code.google.com/p/sregex/ On Wed, Nov 4, 2009 at 6:17 AM, kenny lu wrote:

Michael,

Here is how I do it.

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module Main where

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import Text.Regex.Posix.ByteString import Data.Maybe import qualified Data.ByteString.Char8 as S

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text = S.pack "11\n abcd \n22" p = S.pack "11\n(.*)\n22"

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main :: IO () main = do { (Right pat) <- compile compExtended execBlank p ; res <- regexec pat text ; case res of { (Right (Just (_,_,_,m))) -> putStrLn (show m) ; _ -> putStrLn "not matched." } }

You may swap out ByteString with String, PCRE should be similar, too.

Regards, Kenny

On Wed, Nov 4, 2009 at 2:04 PM, Michael Mossey wrote:

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kenny lu wrote:

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Hi Michael,

Could you give an example of what patterns you want to write?

Regards, Kenny

Something like

text = "11\n abcd \n22" answer = text =~ "11.*22" :: <various possibilities>

and have it find the entire string. The default behavior is to stop matching when it encounters a newline. There is mention in the Text.Regex.Posix docs of a flag to control this behavior, but it is not easy to figure out from the docs how to provide flags. The left-hand side of the =~ is a very complex type.

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