{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# OPTIONS_GHC -fno-warn-tabs #-}

module Hcompta.Expr.If where

import Control.Monad (Monad(..), when)
import Data.Bool

import Hcompta.Expr.Dup

-- * Class 'Expr_If'

class Expr_If repr where
	default if_   :: Monad repr => repr Bool -> repr a -> repr a -> repr a
	default when_ :: Monad repr => repr Bool -> repr () -> repr ()
	
	if_ :: repr Bool -> repr a -> repr a -> repr a
	if_ m ok ko = do
		m' <- m
		if m' then ok else ko
	
	when_ :: repr Bool -> repr () -> repr ()
	when_ m ok = do
		m' <- m
		when m' ok

instance -- Expr_If Dup
 ( Expr_If r1
 , Expr_If r2
 ) => Expr_If (Dup r1 r2) where
	if_ (c1 `Dup` c2) (ok1 `Dup` ok2) (ko1 `Dup` ko2) =
		if_ c1 ok1 ko1 `Dup`
		if_ c2 ok2 ko2
	when_ (c1 `Dup` c2) (ok1 `Dup` ok2) =
		when_ c1 ok1 `Dup`
		when_ c2 ok2