Project Euler - Problem #1

HaskellEuler1.hs

module Euler.Problem1 where

-- | Given a maximum integer m and a factor n calculates the sum
-- of all divisors of the given factor up to m.
sumDivisible :: Int -> Int -> Int
sumDivisible m n = n * (p * (p + 1)) `div` 2 where p = m `div` n

result = (sumDivisible 999 3) + (sumDivisible 999 5) - (sumDivisible 999 15)

solve::String
solve = ("The sum of multiples of 3 and 5 up to 1000 is: " ++ show result)

-- | A naive solution that given two multiples j and k and maximum integer m
--- calculates the sum of all multiples of j and k.
alternative :: Int -> Int -> Int -> Int
alternative j k m = sum [x | x <- [1..m-1], x `mod` j == 0 || x `mod` k == 0]

main = putStrLn solve