Haskell code which multiplies two numbers using addition and bit operations only.

gistfile1.hs

import Data.Bits

-- checks if x is divisble by y
divisible :: Int -> Int -> Bool
divisible x y | y == 2    = not (testBit x 0)
              | otherwise = mod x y == 0

-- multiplies x and y by manipulating bits and performing addition only
mult :: Int -> Int -> Int
mult x y | x == 0              = 0
         | not (divisible x 2) = mult (clearBit x 0) y + y
         | otherwise           = mult (shiftR x 1) (shiftL y 1)