Use functional dependencies.

diff --git a/GHC/Generics.hs b/GHC/Generics.hs
index d2170d9..c1b962d 100644 (file)
--- a/GHC/Generics.hs
+++ b/GHC/Generics.hs
@@ -20,6 +20,7 @@ data (:*:) a b = a :*: b
 {-# OPTIONS_GHC -XTypeSynonymInstances   #-}
 {-# OPTIONS_GHC -XTypeOperators          #-}
 {-# OPTIONS_GHC -XKindSignatures         #-}
 {-# OPTIONS_GHC -XTypeSynonymInstances   #-}
 {-# OPTIONS_GHC -XTypeOperators          #-}
 {-# OPTIONS_GHC -XKindSignatures         #-}

+{-# OPTIONS_GHC -XFunctionalDependencies #-}

 
 module GHC.Generics  (
   -- * Generic representation types
 
 module GHC.Generics  (
   -- * Generic representation types

@@ -34,9 +35,6 @@ module GHC.Generics  (
   , Datatype(..), Constructor(..), Selector(..), NoSelector
   , Fixity(..), Associativity(..), Arity(..), prec
 
   , Datatype(..), Constructor(..), Selector(..), NoSelector
   , Fixity(..), Associativity(..), Arity(..), prec
 

-  -- * Representation type families
-  , Rep0, Rep1
-

   -- * Representable type classes
   , Representable0(..), Representable1(..)
 
   -- * Representable type classes
   , Representable0(..), Representable1(..)
 

@@ -174,18 +172,18 @@ data Associativity =  LeftAssociative
 
 
 -- | Representable types of kind *
 
 
 -- | Representable types of kind *

-class Representable0 a rep where
+class Representable0 a rep | a -> rep where

   -- | Convert from the datatype to its representation
   -- | Convert from the datatype to its representation

-  from0  :: a -> Rep0 a x
+  from0  :: a -> rep x

   -- | Convert from the representation to the datatype
   -- | Convert from the representation to the datatype

-  to0    :: Rep0 a x -> a
+  to0    :: rep x -> a

 
 -- | Representable types of kind * -> *
 
 -- | Representable types of kind * -> *

-class Representable1 f rep where
+class Representable1 f rep | f -> rep where

   -- | Convert from the datatype to its representation
   -- | Convert from the datatype to its representation

-  from1  :: f a -> Rep1 f a
+  from1  :: f a -> rep a

   -- | Convert from the representation to the datatype
   -- | Convert from the representation to the datatype

-  to1    :: Rep1 f a -> f a
+  to1    :: rep a -> f a

 
 --------------------------------------------------------------------------------
 -- Representation for base types
 
 --------------------------------------------------------------------------------
 -- Representation for base types