[Haskell-cafe] multi-line regex

[David Leimbach]

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 <haskellmail at gmail.com> 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 <mpm at alumni.caltech.edu>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.
>>
>>
>>
>>
>>
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>
>
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