Yet Another Haskell Tutorial Ch. 3 Exercise 10 - sum, product, and list of factorials

ch3-10.hs

module Main
    where

import System.IO

main = do
    num <- getNums
    putStrLn ("The sum is " ++ show (sum num))
    putStrLn ("The product is " ++ show (product num))
    putFactorials num

factorial 1 = 1
factorial n = n * factorial (n-1)

putFactorials (n:ns) = do
    putStrLn ((show n) ++ " factorial is " ++ (show (factorial n)))
    if null ns then do
        return []
        else
            putFactorials ns

getNums = do
    putStrLn "Give me a number (or 0 to stop):"
    numStr <- getLine
    let num = read numStr + 0 -- hack; should use types
    if num == 0
        then return []
        else do
            rest <- getNums
            return (num:rest)

out.sh-session

$ ghc --make ch3-10.hs
$ ./ch3-10
Give me a number (or 0 to stop):
5
Give me a number (or 0 to stop):
8
Give me a number (or 0 to stop):
2
Give me a number (or 0 to stop):
0
The sum is 15
The product is 80
5 factorial is 120
8 factorial is 40320
2 factorial is 2