euler1

multipleOf :: (Integral a) => a -> a -> Bool
multipleOf x y
       | mod x y == 0   = True
       | otherwise      = False

sumOfList :: (Num a) => [a] -> a
sumOfList = foldl (+) 0

--| Find the sum of all integers under 1000 that are divisible by 3 or 5.
euler1 = sumOfList $ filter (\x -> x `multipleOf` 3 || x `multipleOf` 5) [999,998..0]