X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=GHC%2FHetMet%2FGArrow.hs;h=e2dbf95d418d4a35d5df5936d990d6d93c397162;hb=11345faf37729b649dad0c052ee698d7080e40ee;hp=b9bfccf922bd745bb64c6d45d6126e056a05d26a;hpb=3b6276233970210dce8d7c12d72ba5d55644e051;p=ghc-base.git

diff --git a/GHC/HetMet/GArrow.hs b/GHC/HetMet/GArrow.hs
index b9bfccf..e2dbf95 100644
--- a/GHC/HetMet/GArrow.hs
+++ b/GHC/HetMet/GArrow.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators -XFunctionalDependencies #-}
+{-# LANGUAGE MultiParamTypeClasses, TypeOperators, FunctionalDependencies, TypeFamilies, FlexibleContexts #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.HetMet.GArrow
@@ -30,8 +30,12 @@ module GHC.HetMet.GArrow (
   GArrowCurry(..),
   GArrowApply(..),
 
-  GArrowKappa(..),
+  GArrowTensor,
+  GArrowUnit,
+  GArrowExponent,
+
   GArrowSTKC(..),
+  GArrowSTKCL(..),
   GArrowSTLC(..),
   GArrowPCF(..)
 
@@ -77,6 +81,8 @@ ga_swap_second f =
 
 
 
+
+
 ------------------------------------------------------------------------
 -- Products, Coproducts, etc
 
@@ -101,8 +107,8 @@ ga_inr = ga_uncancell >>> ga_first  ga_never
 -- Loop
 
 class GArrow g (**) u => GArrowLoop g (**) u where
-  ga_loopl    :: g (x**z) (y**z) -> g x y
-  ga_loopr    :: g (z**x) (z**y) -> g x y
+  ga_loopr    :: g (x**z) (y**z) -> g x y
+  ga_loopl    :: g (z**x) (z**y) -> g x y
 
 
 ------------------------------------------------------------------------
@@ -128,6 +134,8 @@ class GArrow g (**) u => GArrowConstant g (**) u t r where
 
 
 
+
+
 ------------------------------------------------------------------------
 -- Reify and Reflect, which are "curried" versions of eval/const
 
@@ -143,18 +151,6 @@ class GArrow g (**) u => GArrowReflect g (**) u r q x y where
 
 
 
-------------------------------------------------------------------------
--- The Kappa adjunction
---
--- See Hasegawa, Decomposing Typed Lambda Calculus into a Couple of
--- Categorical Programming Languages) section 3, rule $(\times L)$
-
-class GArrow g (**) u => GArrowKappa g (**) u where
-  ga_kappa :: (g u x -> g u y) -> g x y
-
-
-
-
 
 ------------------------------------------------------------------------
 -- Apply and Curry
@@ -170,6 +166,31 @@ class GArrow g (**) u => GArrowCurry g (**) u (~>) where
 
 
 
+
+------------------------------------------------------------------------
+-- Type Families
+
+--
+-- The GArrow and GArrow{Copy,Drop,Swap} classes brandish their tensor
+-- and unit types; this is important because we might want to have
+-- both "instance GArrow g X Y" and "instance GArrow g Z Q" -- in
+-- fact, this is exactly how sums and pairs are defined.
+--
+-- However, in daily practice it's a pain to have all those extra type
+-- variables floating around.  If you'd like to hide them, you can use
+-- the type families below to do so; see the definition of class
+-- GArrowSTKC for an example.  Keep in mind, however, that any given
+-- type may only have a single instance declared using the type
+-- families.
+--
+
+type family GArrowTensor   g :: * -> * -> *   -- (**)
+type family GArrowUnit     g :: *             -- ()
+type family GArrowExponent g :: * -> * -> *   -- (~>)
+
+
+
+
 ------------------------------------------------------------------------
 -- Commonly Implemented Collections of Classes
 
@@ -178,21 +199,36 @@ class GArrow g (**) u => GArrowCurry g (**) u (~>) where
 -- Lambda Calculus into a Couple of Categorical Programming
 -- Languages__, http://dx.doi.org/10.1007/3-540-60164-3_28
 -- 
-class (GArrowDrop  g (**) u,
-       GArrowCopy  g (**) u,
-       GArrowSwap  g (**) u) =>
-       GArrowSTKC  g (**) u
+
+class (GArrowDrop  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCopy  g (GArrowTensor g) (GArrowUnit g),
+       GArrowSwap  g (GArrowTensor g) (GArrowUnit g)) =>
+       GArrowSTKC  g
+
+class (GArrowDrop  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCopy  g (GArrowTensor g) (GArrowUnit g),
+       GArrowSwap  g (GArrowTensor g) (GArrowUnit g),
+       GArrowLoop  g (GArrowTensor g) (GArrowUnit g)) =>
+       GArrowSTKCL  g
 
 -- The simply typed LAMBDA calculus
-class (GArrowSTKC  g (**) u,
-       GArrowCurry g (**) u (~>),
-       GArrowApply g (**) u (~>)) =>
-       GArrowSTLC  g (**) u (~>)
+class (GArrowDrop  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCopy  g (GArrowTensor g) (GArrowUnit g),
+       GArrowSwap  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCurry g (GArrowTensor g) (GArrowUnit g) (GArrowExponent g),
+       GArrowApply g (GArrowTensor g) (GArrowUnit g) (GArrowExponent g)
+       ) =>
+       GArrowSTLC  g
 
 -- Programming Language for Computable Functions (w/o integers and booleans)
-class (GArrowSTLC  g (**) u (~>),
-       GArrowLoop  g (**) u) =>
-       GArrowPCF   g (**) u (~>)
+class (GArrowDrop  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCopy  g (GArrowTensor g) (GArrowUnit g),
+       GArrowSwap  g (GArrowTensor g) (GArrowUnit g),
+       GArrowCurry g (GArrowTensor g) (GArrowUnit g) (GArrowExponent g),
+       GArrowApply g (GArrowTensor g) (GArrowUnit g) (GArrowExponent g),
+       GArrowLoop  g (GArrowTensor g) (GArrowUnit g)
+      ) =>
+      GArrowPCF   g (**) u (~>)