mykatas/haskell/9_title_case.hs

module TitleCase (titleCase) where

import qualified Data.Char as Char

titleCase :: String -> String -> String
titleCase minor = unwords . process . words . toLower
  where
    process :: [String] -> [String]
    process []          = []
    process (head:tail) = toTitle head : map maybeToTitle tail

    lowerMinorWords :: [String]
    lowerMinorWords = words $ toLower minor

    maybeToTitle :: String -> String
    maybeToTitle word
      | word `elem` lowerMinorWords = word
      | otherwise                   = toTitle word

toTitle :: String -> String
toTitle []          = []
toTitle (head:tail) = Char.toUpper head : toLower tail

toLower :: String -> String
toLower = map Char.toLower