improve comments in GHC.HetMet.GArrow

diff --git a/GHC/HetMet/GArrow.hs b/GHC/HetMet/GArrow.hs
index d31436c..da6a9c2 100644 (file)
--- a/GHC/HetMet/GArrow.hs
+++ b/GHC/HetMet/GArrow.hs
@@ -1,4 +1,14 @@
-{-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators #-}
+{-# OPTIONS -XRankNTypes -XMultiParamTypeClasses -XNoMonomorphismRestriction -XTypeOperators -XFlexibleInstances #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  GHC.HetMet.GArrow
+-- Copyright   :  none
+-- License     :  public domain
+--
+-- Maintainer  :  Adam Megacz <megacz@acm.org>
+-- Stability   :  experimental
+-- Portability :  portable
+
 module GHC.HetMet.GArrow (
   GArrow(..),
   GArrowDrop(..),
@@ -8,6 +18,7 @@ module GHC.HetMet.GArrow (
   GArrowReify(..),
   GArrowReflect(..)
 ) where
+import Control.Arrow
 
 class GArrow g (**) where
   ga_id        :: g x x
@@ -28,8 +39,10 @@ class GArrow g (**) => GArrowCopy g (**) where
   ga_copy      :: g x (x**x)
 
 class GArrow g (**) => GArrowSwap g (**) where
-  ga_swap      :: g (x**y) (y**x)
-  --ga_second  f =  ga_comp (ga_comp ga_swap (ga_first f)) ga_swap
+  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
 
 class GArrow g (**) => GArrowLoop g (**) where
   ga_loop      :: g (x**z) (y**z) -> g x y
@@ -37,12 +50,13 @@ class GArrow g (**) => GArrowLoop g (**) where
 class GArrow g (**) => GArrowLiteral g (**) a where
   ga_literal   :: a -> g () a
 
--- not sure
+-- not sure -- subject to change
 class GArrow g (**) => GArrowReify g (**) where
   ga_reify     :: (x -> y) -> g x y
 
--- not sure
+-- not sure -- subject to change
 class GArrow g (**) => GArrowReflect g (**) where
   ga_reflect   :: g x y -> (x -> y)
 
 
+