1HaskellADay: appendSwapped

appendSwapped.hs

import Control.Applicative
import Data.Tuple (swap)

{- Given a list of tuples, return a list containing the initial elements and the swapped elements
   It's an easy one to start the week.

   Example
   > appendSwapped [(1,2),(2,3)]
   [(1,2),(2,3),(2,1),(3,2)]
-}

appendSwapped :: [(a, a)] -> [(a, a)]
appendSwapped = ([id, swap] <*>)

-- Find a similar process for an entry type: [(a,b)]
appendSwapped' :: [(a,b)] -> [Either (a,b) (b,a)]
appendSwapped' = ([Left, Right . swap] <*>)