Arrows

Example.hs

{-# LANGUAGE Arrows #-}

import Control.Arrow

double :: Int -> Int
double x = x * 2

triple :: Int -> Int
triple x = x * 3

increment :: Int -> Int
increment x = x + 1

combine :: Int -> Int
combine =
    ( double &&& increment
        >>^ (\(x, y) -> x + y)
    ) &&& triple >>^ (\(x, y) -> x + y)

combine' :: Int -> Int
combine' = proc x -> do
    a <- double -< x
    b <- increment -< x
    c <- triple -< x
    returnA -< a + b + c