-- a small exercise:
-- how many words are there in a string

import Char

countWords :: String -> Int

data WordFlag = InWord |
                BetweenWords
     deriving Eq

type ParseState = (WordFlag, Int)

countWordsCore :: String -> ParseState -> (ParseState, String)

countWordsCore "" parsestate = (parsestate, "")

countWordsCore string parsestate = countWordsCore stringTail (newFlag, newCount)
    where charHead:stringTail = string
          (flag, count) = parsestate
          isHeadAlpha = isAlpha charHead
          newFlag | isHeadAlpha = InWord
                  | otherwise   = BetweenWords
          newCount | isHeadAlpha && (flag == BetweenWords) = count + 1
                   | otherwise                             = count

countWords string = count
    where ((_, count), _) = countWordsCore string (BetweenWords, 0)

main = do putStrLn "enter a text, complete with Enter"
          string <- getLine
          print (countWords string)