poemlines.hs

module PoemLines where

firstSen = "Tyger Tyger, burning bright\n"
secondSen = "In the forests of the night\n"
thirdSen = "What immortal hand or eye\n"
fourthSen = "Could frame thy fearful symmetry?"
sentences = firstSen ++ secondSen ++ thirdSen ++ fourthSen

notNewLine :: Char -> Bool
notNewLine = (/=)'\n'

myLines :: String -> [String]
myLines s = go s []
  where go [] xs = xs
        go s' xs = go rest $ xs ++ [nextWord]
          where nextWord   = (takeWhile notNewLine s')
                rest       = drop 1 (dropWhile notNewLine s')

myLinesOn :: (Eq a) => [a] -> a -> [[a]]
myLinesOn s c = go s []
  where pred     = (/=)c
        go [] xs = xs
        go s' xs = go rest result
          where nextWord   = (takeWhile pred s')
                result     = xs ++ [nextWord]
                rest       = drop 1 (dropWhile pred s')


shouldEqual =
  [ "Tyger Tyger, burning bright"
  , "In the forests of the night"
  , "What immortal hand or eye"
  , "Could frame thy fearful symmetry?"
  ]

main :: IO ()
main =
  print $ "Are they equal?" ++ show (myLines sentences == shouldEqual)