[Haskell-cafe] Re: Software Tools in Haskell
apfelmus at quantentunnel.de
Wed Dec 12 15:43:55 EST 2007
Tommy M McGuire wrote:
> (Plus, interact is scary. :-D )
You have a scary feeling for a moment, then it passes. ;)
> Gwern Branwen wrote:
>> I... I want to provide a one-liner for 'detab', but it looks
>> impressively monstrous and I'm not sure I understand it.
> On the other hand, I'm not looking for one-liners; I really want clarity
> as opposed to cleverness.
tabwidth = 4
-- tabstop !! (col-1) == there is a tabstop at column col
-- This is an infinite list, so no need to limit the line width
tabstops = map (\col -> col `mod` tabwidth == 1) [1..]
-- calculate spaces needed to fill to the next tabstop in advance
tabspaces = snd $ mapAccumR addspace  tabstops
addspace cs isstop = let cs'=' ':cs in (if isstop then  else cs',cs')
main = interact $ unlines . map detabLine . lines
detabLine = concat $ zipWith replace tabspaces
replace cs '\t' = cs -- replace with adequate number of spaces
replace _ char = [char] -- pass through
How about that?
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