On Dec 13, 2007 2:28 AM, Benja Fallenstein
Although on reflection, I think I might like the following compromise with Tillmann's version best:
main = interact $ perLine $ detab 0 where detab tab ('\t':cs) = replicate (4-tab) ' ' ++ detab 0 cs detab tab (char:cs) = char : detab ((tab+1) `mod` 4) cs detab tab "" = ""
On more reflection, I wonder whether it would be worthwhile to have a library function for folds that work from both left *and* right: foldlr :: (a -> b -> c -> (a,c)) -> a -> c -> [b] -> (a,c) foldlr f l r [] = (l,r) foldlr f l r (x:xs) = let (l',r') = f l x r''; (l'',r'') = foldlr f l' r xs in (l'',r') main = interact $ perLine $ snd . foldlr detab 0 "" where detab tab '\t' cs = (0, replicate (4-tab) ' ' ++ cs) detab tab char cs = ((tab+1) `mod` 4, char : cs) It's a fun function, anyway :-) - Benja