[Haskell-cafe] cutting long strings into lines

[Bertram Felgenhauer]

Matthias Fischmann wrote:
> 
> On Sat, Sep 30, 2006 at 11:54:19AM -0400, Mark T.B. Carroll wrote:
> > module WordWrap (wrap) where
> > import Data.Maybe
> > 
> > options :: String -> [(String, String)]
> > 
> > options [] = [("", "")]
> > 
> > options (x:xs) =
> >     let rest = map (\(ys, zs) -> (x:ys, zs)) (options xs)
> >      in if x == ' ' then ("", xs) : rest else rest
> > 
> > bestSplit :: Int -> String -> (String, String)
> > 
> > bestSplit width string =
> >     last (head wraps : takeWhile ((<= width) . length . fst) (options string))
> 
> Works better if you just skip the "head wraps" part.  (and now i am
> curious: what was it supposed to mean?  how did it get there?)

I'll venture a guess: The code originally read

| bestSplit width string =
|     let wraps = options string
|     in  last (head wraps : takeWhile ((<= width) . length . fst) wraps)

Without a precaution like this, long words will cause wrap to go into an
infinite loop. Depending on your requirements you could also consider

| bestSplit width string =
|     last (splitAt width string : takeWhile ((<= width) . length . fst)
|           (options string))

which will cut too long words into pieces fitting on the lines.

(code untested)

regards,

Bertram