fizzbuzz.hs

import Control.Monad
import Control.Applicative
import Data.Monoid
import Data.Maybe

main :: IO()
main = do
	putStr "results: \n"
	putStr $ fizzbuzz5 20

fizzbuzz :: Int -> String
fizzbuzz to = unlines $ map displayInt [1..to]
	where
	displayInt = fromMaybe . show <*> 3 `displays` "fizz" <> 5 `displays` "buzz"
	(d `displays` s) n = if n `mod` d == 0 then Just s else Nothing

fizzbuzz2 :: Int -> String
fizzbuzz2 to = unlines $ map displayInt [1..to]
	where
	displayInt n = fromMaybe (show n) $ mfilter (not . null) (Just (fizz ++ buzz))
		where
		fizz = testInt 3 "fizz"
		buzz = testInt 5 "buzz"
		testInt d s = if n `mod` d == 0 then s else ""

fizzbuzz3 :: Int -> String
fizzbuzz3 to = unlines $ map displayInt [1..to]
	where
	displayInt n = fromMaybe (show n) (msum [liftM2 (++) fizz buzz, fizz, buzz])
		where
		fizz = testInt 3 "fizz"
		buzz = testInt 5 "buzz"
		testInt d s = if n `mod` d == 0 then Just s else Nothing

data Output = Fizz | Buzz | Num
fizzbuzz4 :: Int -> String
fizzbuzz4 n = unlines $ zipWith3 test (cycle [Num, Num, Fizz]) (cycle [Num, Num, Num, Num, Buzz]) [1..n]
	where
	test Fizz Buzz _ = "fizzbuzz"
	test Fizz _ _ = "fizz"
	test _ Buzz _ = "buzz"
	test _ _ num = show num

fizzbuzz5 :: Int -> String
fizzbuzz5 to = unlines $ zipWith3 test (pat 3 "fizz") (pat 5 "buzz") [1..to]
	where
	pat n str = cycle (replicate (n - 1) "" ++ [str])
	test s1 s2 n = head $ ((<$) <*> guard . not . null) (s1 ++ s2) ++ [show n]

fizzbuzz6 :: Int -> String
fizzbuzz6 to = unlines $ map displayInt [1..to]
	where
	displayInt n = if null fizz_or_buzz then show n else fizz_or_buzz
		where
		fizz_or_buzz = testInt 3 "fizz" ++ testInt 5 "buzz"
		testInt d s = if n `mod` d == 0 then s else ""