Beer.hs

main :: IO ()
main = mapM_ putStrLn beerLines
  where
    beerLines = concatMap genLines [99, 98..1]

    genLines n =
      [ firstLine n
      , "Take one down, pass it around, " ++ suffix n
      ]

    firstLine 1 = "1 bottle of beer on the wall, 1 bottle of beer."
    firstLine n = show n ++ " bottles of beer on the wall, "
                         ++ show n ++ " bottles of beer."

    suffix 1 = "no more beer on the wall!"
    suffix 2 = "1 bottle of beer on the wall"
    suffix n = show (n - 1) ++ " bottles of beer on the wall"