Initial commit

import System.Environment

type Buzzword = (Integer, String)

buzzwords :: [Buzzword]

buzzwords = [(3, "Fizz"), (5, "Buzz")]

fizzbuzz :: [Either String Integer]

fizzbuzz = fizzeval `map` [1 ..]

fizzeval :: Integer -> Either String Integer

fizzeval x = if null str then Right int else Left str

             where (int, str) = foldl fizztest (x, "") buzzwords

fizztest :: Buzzword -> Buzzword -> Buzzword

fizztest (x, xstr) (y, ystr) = if y `divides` x then (x, xstr ++ ystr) else (x, xstr)

divides :: Integer -> Integer -> Bool

y `divides` x = x `mod` y == 0

-- This place is not a place of honor... no highly esteemed deed is commemorated here...

-- nothing valued is here. What is here is dangerous and repulsive to us.

-- This message is a warning about the IO Monad.

-- The Monad is in a particular location...

-- it increases toward the main... the center of danger is here...

-- of a particular size and shape, and below us.

say :: Either String Integer -> IO ()

say (Right x) = print x

say (Left x) = putStrLn x

sayNum :: Maybe Int -> IO ()

sayNum Nothing  = say `foldMap` fizzbuzz

sayNum (Just n) = say `foldMap` (take n fizzbuzz)

parseArgs :: [String] -> IO (Maybe Int)

parseArgs args =

    if null args then pure Nothing else pure int

    where int = if null parsed || (not $ null $ snd $ head parsed)

                   then Nothing

                   else Just $ fst $ head parsed

                where parsed = reads $ head args :: [(Int, String)]

main :: IO ()

main = getArgs >>= parseArgs >>= sayNum