An implementation of FizzBuzz inspired by a Tom Scott video

fizzbuzz.hs

-- borrowed from FSharp
(|>) :: t -> (t -> t1) -> t1
a |> b = b a

-- The game rules:
fizzbuzz :: Integer -> String
fizzbuzz n = let
      -- We can create rules that process numbers.
      -- The incoming numbers are paired with an accumulated String
      rule :: Integer -> String -> (Integer, Maybe String) -> (Integer, Maybe String)
      rule num word (i, acc) | (i `mod` num) /= 0 = (i, acc)
                             | acc == Nothing     = (i, Just word)
                             | otherwise          = (i, fmap (++ word) acc)

      -- The final step always produces a string, either from the accumulator or the index
      showNumberOtherwise :: (Integer, Maybe String) -> String
      showNumberOtherwise (_, Just word) = word
      showNumberOtherwise (i, _)         = show i
   in
      (n, Nothing) |> rule 3 "Fizz" |> rule 5 "Buzz" |> showNumberOtherwise

-- Process the numbers from 1..100 and print the results
main :: IO ()
main = mapM_ putStrLn $ map fizzbuzz [1..100]

-- vim: et