On Sat, Aug 14, 2010 at 12:33 PM, Bill Atkins
Try this one (http://gist.github.com/524460)
I noticed that Bill's solution doesn't seem to work if the input text is infinite. I found a different solution, which avoids the use of reverse, and will work even if the input is infinite, as long as the words themselves are finite in length. (http://hpaste.org/fastcgi/hpaste.fcgi/view?id=29048) module Main where import Data.List combineNonEmpty :: (t -> Bool) -> t -> ([t] -> t) -> [t] -> [t] combineNonEmpty isNull zero cat [] = [] combineNonEmpty isNull zero cat xs = let (ys, zs) = break isNull xs rest = if null zs then [] else zero : combineNonEmpty isNull zero cat (tail zs) in if null ys then rest else cat ys : rest textToParagraphs :: String -> [String] textToParagraphs = combineNonEmpty null [] (concat . intersperse' " ") . lines intersperse' :: a -> [a] -> [a] intersperse' a [] = [] intersperse' a (x:xs) = x : (if null xs then [] else a : intersperse' a xs) wordWrap :: Int -> [String] -> [[String]] wordWrap maxLineLength [] = [] wordWrap maxLineLength ws = let lengths = scanl1 (\a b -> a + b + 1) $ map length ws wordCount = length $ takeWhile (<= maxLineLength) lengths wordCount' = if wordCount >= 1 then wordCount else 1 (xs, rest) = splitAt wordCount' ws in xs : wordWrap maxLineLength rest wrapParagraph :: Int -> String -> [String] wrapParagraph maxLineLength str = let ws = words str in if null ws then [""] else map unwords $ wordWrap maxLineLength ws wrapText :: Int -> String -> String wrapText maxLineLength = unlines . concat . map (wrapParagraph maxLineLength) . textToParagraphs main :: IO () main = interact (wrapText 72)