Separate.hs

{-# LANGUAGE ScopedTypeVariables #-}

import Data.Maybe

swords :: String -> Bool
swords "hello" = True
swords "my" = True
swords "sam" = True
swords _ = False

check :: (String, String) -> Maybe String
check (prefix, suffix) =
  if swords prefix
  then if suffix == ""
        then Just prefix
        else fmap ((prefix ++ " ") ++) (separate suffix)
  else Nothing

separate :: String -> Maybe String
separate "" = Just ""
separate s = listToMaybe $ mapMaybe check splits
  where splits = map (`splitAt` s) [0..length s]