Initial commit

fizzbuzz.hs

+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