euler1

-- 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.

foldr1 (+) [c | c <- [1..1000], ((c `mod` 3) == 0) && ((c `mod` 5) == 0)]