Main.purs

module Main where

import Prelude
import Data.Either
import Data.Functor.Compose
import Control.Monad.Eff.Console (print)

class Convert a b where
  convert :: a -> b

data A = A Int Int
type B = Array Int

instance convertId :: Convert a a where
  convert = id

instance convertA :: Convert (Array Int) A where
  convert [x,y] = A x y

instance convertChain :: (Convert b a, Convert r r') => Convert (a -> r) (b -> r') where
  convert a2r b = convert (a2r (convert b))

f :: A -> A -> Int
f (A a b) (A c d) = a + b + c + d

g :: B -> B -> Int
g = convert f

f' :: A -> A -> A -> A -> Int
f' a b c d = f a b + f c d

g' :: B -> B -> B -> B -> Int
g' = convert f'

main = print (g' [1,2] [3,4] [5,6] [7,8])