>>> What's an elegant definition of a Haskell function that takes two strings >>> and returns "Nothing" in case the first string isn't a substring of the >>> first, or "Just i", where i is the index number of the position within the >>> first string where the second string begins?
my quick take, with Maybe and fmap : substringP :: String -> String -> Maybe Int substringP _ [] = Nothing substringP sub str = case isPrefixOf sub str of False -> fmap (+1) $ substringP sub (tail str) True -> Just 0 -- Paul _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
