Multiples of 3 and 5

main.hs

-- If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
-- Find the sum of all the multiples of 3 or 5 below 1000.

rec_sum []     = 0
rec_sum (x:xs) = x + rec_sum xs

nums = [(x::Integer) | x <- [1..999], x `mod` 3 == 0 || x `mod` 5 == 0]
total = rec_sum nums

main = do
    print nums 
    print total