Thanks Carlos - you can import Text.Regex.Posix to get (=~)

Is there a way to avoid the (++) in your implementation? It has a linear time overhead.

Regards,

Kashyap

On Mon, Jul 16, 2012 at 1:36 AM, Carlos J. G. Duarte <carlos.j.g.duarte@gmail.com> wrote:

Looks good to me, but I'm just a beginner!
I used the isInfixOf from Data.List instead of =~ to run your example because the later wasn't working on my instalation.

I've made a slightly variant using the break function:

import Data.List

startTag = "<bug>"
endTag = "</bug>"

main = interact process

process  = unlines . extractSection startTag endTag . lines
extractSection start stop xs =
  let (ls,rs) = break (isInfixOf stop) $ dropWhile (not . isInfixOf start) xs
  in ls ++ take 1 rs

On 07/15/12 13:08, C K Kashyap wrote:

Hi,

I've written a small haskell program to extract a section from a file between start and end markers. For example, if I have a file such as below - 

a

b

c

        <bug>

d

e

f

        </bug>

g

h

i

I'd like to extract the contents between <bug> and </bug> (including the markers). 

startTag = "<bug>"
endTag = "</bug>"

process  = unlines . specialTakeWhile (f endTag) . dropWhile (f startTag) . lines 
        where f t x = not (x =~ t) 
              specialTakeWhile :: (a -> Bool) -> [a] -> [a]
              specialTakeWhile ff [] = []
              specialTakeWhile ff (x:xs) = if ff x then x:(specialTakeWhile ff xs) else [x]

It'll be great if I could get some feedback on this.

Regards,

Kashyap

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