Ex 2 on Page 447

Page447.hs

module Page447 where

import Data.Char

capitalizeWord :: String -> String
capitalizeWord (c:cs) = toUpper c : cs

endsWithPeriod :: String -> Bool
endsWithPeriod word = last word == '.'

capitalizeParagraph :: String -> String
capitalizeParagraph para = unwords (go (words para) True)
  where
    go [] _ = []
    go (word:words) capIt = wordCapped : go words (endsWithPeriod word)
      where wordCapped = if capIt then (capitalizeWord word) else word