-{-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators -XFlexibleInstances #-}
+{-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators -XFlexibleInstances -XFunctionalDependencies #-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.HetMet.GArrow
import Control.Arrow
import Control.Category
-class GArrow g (**) where
- ga_id :: g x x
- ga_comp :: g x y -> g y z -> g x z
+class Category g => GArrow g (**) | g -> (**) where
ga_first :: g x y -> g (x ** z) (y ** z)
ga_second :: g x y -> g (z ** x) (z ** y)
ga_cancell :: g (()**x) x
ga_swap :: g (x**y) (y**x)
-- implementation of ga_second for GArrowSwap instances
-ga_swap_second f = ga_comp (ga_comp ga_swap (ga_first f)) ga_swap
+ga_swap_second f = ga_swap >>> ga_first f >>> ga_swap
class GArrow g (**) => GArrowLoop g (**) where
ga_loop :: g (x**z) (y**z) -> g x y
-- GArrow instances for Control.Arrow
instance Arrow a => GArrow a (,) where
- ga_id = arr Prelude.id
- ga_comp = (>>>)
ga_first = first
ga_second = second
ga_cancell = arr (\((),x) -> x)
instance Arrow a => GArrowSwap a (,) where
ga_swap = arr (\(x,y) -> (y,x))
-instance Arrow a => GArrowLiteral a (,) where
+instance Arrow a => GArrowLiteral a (,) b where
ga_literal x = arr (\() -> x)
instance Arrow a => GArrowReify a (,) where
-------------------------------------------------------------------------------
--- Category instance for GArrow
-
-instance GArrow g => Category g where
- id = ga_id
- x .y = ga_comp y x
-
-
-