multi-line regex

Michael Mossey

4 Nov 2009 4 Nov '09

5:35 a.m.

I have some very simple regex-matching needs, and Text.Regex.Posix will work fine, EXCEPT I need to match multi-line patterns, and/or find all occurrences of text that may occur several times on different lines. So I need to turn on some kind of flag. Can someone show me how to do that? I have worked the examples in RWH so I basically know how to run the thing.

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Don Stewart

4 Nov 4 Nov

5:45 a.m.

mpm:

...

I have some very simple regex-matching needs, and Text.Regex.Posix will work fine, EXCEPT I need to match multi-line patterns, and/or find all occurrences of text that may occur several times on different lines. So I need to turn on some kind of flag. Can someone show me how to do that? I have worked the examples in RWH so I basically know how to run the thing.

Is that something that requires the PCRE bindings?

kenny lu

5:48 a.m.

Hi Michael, Could you give an example of what patterns you want to write? Regards, Kenny On Wed, Nov 4, 2009 at 1:35 PM, Michael Mossey wrote:

...

I have some very simple regex-matching needs, and Text.Regex.Posix will work fine, EXCEPT I need to match multi-line patterns, and/or find all occurrences of text that may occur several times on different lines. So I need to turn on some kind of flag. Can someone show me how to do that? I have worked the examples in RWH so I basically know how to run the thing. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Michael Mossey

6:04 a.m.

kenny lu wrote:

...

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.

kenny lu

2:17 p.m.

Michael, Here is how I do it.

...

module Main where

...

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

...

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

...

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:

...

kenny lu wrote:

...
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.

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

David Leimbach

3:30 p.m.

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.pdf http://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.

...
module Main where

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

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

...
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:

...
kenny lu wrote:

...
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.

_______________________________________________ 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

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David Leimbach
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multi-line regex

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