{-# LANGUAGE OverlappingInstances #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE GADTs #-}

module MyLang where

import Prelude (Integer(..), Show(..),String(..))
import qualified Prelude as P

import Generic.Data.Bool
import Generic.Data.Num

data MyLang a where
  MLFalse :: MyLang Bool
  MLTrue  :: MyLang Bool
  MLValue :: a -> MyLang a

instance BoolC MyLang where
  false = MLFalse
  true  = MLTrue
  bool t _ MLTrue  = t
  bool _ e MLFalse = e

instance Num MyLang Integer where
  fromInteger = MLValue
  (MLValue a) + (MLValue b) = MLValue (a P.+ b)
  (MLValue a) - (MLValue b) = MLValue (a P.- b)
  (MLValue a) * (MLValue b) = MLValue (a P.* b)

test :: MyLang Integer
test = if' true (3 + 4) (4)