Elegant fizzbuzz implementation based on Monoids. Inspired by http://www.parsonsmatt.org/2016/02/27/an_elegant_fizzbuzz.html.

ElegantFizzBuzz.hs

module Main where

import Data.Foldable (fold)
import Data.Maybe (fromMaybe, listToMaybe)

fizzBuzz :: Functor f => f Int -> f String
fizzBuzz =
    fmap (fromMaybe <$> show <*> fold rules)
  where
    rules = [fizz, buzz]
    fizz = rule "Fizz" 3
    buzz = rule "Buzz" 5
    rule str n i = listToMaybe [ str | i `mod` n == 0 ]
        
main :: IO ()
main =
    mapM_ putStrLn (fizzBuzz [1..20])