1 {-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators -XFlexibleInstances -XFunctionalDependencies #-}
2 -----------------------------------------------------------------------------
4 -- Module : GHC.HetMet.GArrow
6 -- License : public domain
8 -- Maintainer : Adam Megacz <megacz@acm.org>
9 -- Stability : experimental
10 -- Portability : portable
12 module GHC.HetMet.GArrow (
22 import Control.Category
24 class Category g => GArrow g (**) | g -> (**) where
25 ga_first :: g x y -> g (x ** z) (y ** z)
26 ga_second :: g x y -> g (z ** x) (z ** y)
27 ga_cancell :: g (()**x) x
28 ga_cancelr :: g (x**()) x
29 ga_uncancell :: g x (()**x)
30 ga_uncancelr :: g x (x**())
31 ga_assoc :: g ((x**y)**z) (x**(y**z))
32 ga_unassoc :: g (x**(y**z)) ((x**y)**z)
34 class GArrow g (**) => GArrowDrop g (**) where
37 class GArrow g (**) => GArrowCopy g (**) where
40 class GArrow g (**) => GArrowSwap g (**) where
41 ga_swap :: g (x**y) (y**x)
43 -- implementation of ga_second for GArrowSwap instances
44 ga_swap_second f = ga_swap >>> ga_first f >>> ga_swap
46 class GArrow g (**) => GArrowLoop g (**) where
47 ga_loop :: g (x**z) (y**z) -> g x y
49 class GArrow g (**) => GArrowLiteral g (**) a where
50 ga_literal :: a -> g () a
52 -- not sure -- subject to change
53 class GArrow g (**) => GArrowReify g (**) where
54 ga_reify :: (x -> y) -> g x y
56 -- not sure -- subject to change
57 class GArrow g (**) => GArrowReflect g (**) where
58 ga_reflect :: g x y -> (x -> y)
62 ------------------------------------------------------------------------------
63 -- GArrow instances for Control.Arrow
65 instance Arrow a => GArrow a (,) where
68 ga_cancell = arr (\((),x) -> x)
69 ga_cancelr = arr (\(x,()) -> x)
70 ga_uncancell = arr (\x -> ((),x))
71 ga_uncancelr = arr (\x -> (x,()))
72 ga_assoc = arr (\((x,y),z) -> (x,(y,z)))
73 ga_unassoc = arr (\(x,(y,z)) -> ((x,y),z))
75 instance Arrow a => GArrowDrop a (,) where
76 ga_drop = arr (\x -> ())
78 instance Arrow a => GArrowCopy a (,) where
79 ga_copy = arr (\x -> (x,x))
81 instance Arrow a => GArrowSwap a (,) where
82 ga_swap = arr (\(x,y) -> (y,x))
84 instance Arrow a => GArrowLiteral a (,) b where
85 ga_literal x = arr (\() -> x)
87 instance Arrow a => GArrowReify a (,) where
90 instance ArrowLoop a => GArrowLoop a (,) where