fizzbuzz1.hs

fizzbuzz :: Int -> String
fizzbuzz n = unlines $ map fizzbuzz' [1 .. n] 
  where
    fizzbuzz' n = let p = n `mod` 3 == 0
                      q = n `mod` 5 == 0
                  in case (p, q) of
                    (p, q) | p && q    -> "FizzBuzz"
                           | p         -> "Fizz"
                           | q         -> "Buzz"
                           | otherwise -> show n

main = putStr $ fizzbuzz 50

fizzbuzz2.hs

fizzbuzz :: Int -> String
fizzbuzz n = unlines $ map fizzbuzz' [1 .. n]
  where
    fizzbuzz' n = f $ fizz ++ buzz
      where 
        fizz = if n `mod` 3 == 0 then "Fizz" else ""
        buzz = if n `mod` 5 == 0 then "Buzz" else ""
        f [] = show n
        f (x:xs) = (x:xs)

main = (putStr . fizzbuzz) 100

fizzbuzz3.hs (based on fizzbuzz1.hs):

fizzbuzz :: Int -> String
fizzbuzz n = unlines $ map fizzbuzz' [1 .. n]
    where
        fizzbuzz' n = case (n `mod` 3, n `mod` 5) of
            (0, 0) -> "FizzBuzz"
            (0, _) -> "Fizz"
            (_, 0) -> "Buzz"
            (_, _) -> show n

main = putStr $ fizzbuzz 50

fizzbuzz4.hs:

fizzbuzz :: Int -> String
fizzbuzz n = unlines $ map fizzbuzz' [1 .. n]
    where
        fizzbuzz' n = defaultTo (show n) $ concat $ consIf (n `mod` 3 == 0) "Fizz" $ consIf (n `mod` 5 == 0) "Buzz" $ []

        consIf :: Bool -> a -> [a] -> [a]
        consIf False _ xs = xs
        consIf True  x xs = x : xs

        defaultTo :: [a] -> [a] -> [a]
        defaultTo ys [] = ys
        defaultTo _  xs = xs


main = putStr $ fizzbuzz 50

I think that consIf and defaultTo can be useful in other circumstances.

Thanks for the tip! It became more simple. :)

They were my first Haskell programs..