Simple examples of useful functions from Control.Arrow, via the very helpful https://en.wikibooks.org/wiki/Haskell/Understanding_arrows

ArrowExamples.hs

module ArrowExamples where

import Control.Arrow

-- Based on https://en.wikibooks.org/wiki/Haskell/Understanding_arrows

-- function composition:

composed :: Int -> Int
composed = succ >>> (*3)

-- composed 1 = 6

-- Operations on pairs of values:

-- first and second pass through one of the elements of the pair unchanged:

incrementFirst :: (Int, Int) -> (Int, Int)
incrementFirst = first succ

-- incrementFirst (1,2) = (2,2)

--- other operations operate on both elements, but independently:

opposite :: (Int, Int) -> (Int, Int)
opposite = succ *** pred

-- opposite (1,1) = (2,0)

-- copy the input to form a pair:
fork :: Int -> (Int, Int)
fork = succ &&& pred

-- fork 1 = (2,0)