fb.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

import Data.Monoid

newtype On = On [(Int, String)] deriving Monoid
on n s = On [(n, s)]

messages (On x) = cycle $ map funcFor [1..maxM]
    where
        maxM = foldl1 lcm $ map fst x
        funcFor m = case buildMessage of
            [] -> show
            s  -> const s
            where buildMessage = concat [ s | (n, s) <- x, m `mod` n == 0 ]

printMessages = mapM_ (\(n, f) -> putStrLn $ f n) . zip [1..]
run = printMessages . messages

main = run $ on 3 "Fizz" <> on 5 "Buzz" <> on 4 "Kak"