X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FArrow.hs;h=f3c1de2f3b9ca9e5887446c2a64ec42285891fbe;hb=d92335309378a55fcd85074bbe9b4d7ff6fdba8b;hp=ed9fa734b108e7c51727c44529a896f2257edcf1;hpb=10e529099e84e0270da4228132e27f0adae638b5;p=ghc-base.git

diff --git a/Control/Arrow.hs b/Control/Arrow.hs
index ed9fa73..f3c1de2 100644
--- a/Control/Arrow.hs
+++ b/Control/Arrow.hs
@@ -39,7 +39,6 @@ module Control.Arrow (
         ) where
 
 import Prelude hiding (id,(.))
-import qualified Prelude
 
 import Control.Monad
 import Control.Monad.Fix
@@ -54,20 +53,16 @@ infixr 1 ^>>, >>^
 infixr 1 ^<<, <<^
 
 -- | The basic arrow class.
---   Any instance must define either 'arr' or 'pure' (which are synonyms),
---   as well as 'first'.  The other combinators have sensible
---   default definitions, which may be overridden for efficiency.
+--
+--   Minimal complete definition: 'arr' and 'first'.
+--
+--   The other combinators have sensible default definitions,
+--   which may be overridden for efficiency.
 
 class Category a => Arrow a where
 
-        -- | Lift a function to an arrow: you must define either this
-        --   or 'pure'.
+        -- | Lift a function to an arrow.
         arr :: (b -> c) -> a b c
-        arr = pure
-
-        -- | A synonym for 'arr': you must define one or other of them.
-        pure :: (b -> c) -> a b c
-        pure = arr
 
         -- | Send the first component of the input through the argument
         --   arrow, and copy the rest unchanged to the output.
@@ -98,8 +93,6 @@ class Category a => Arrow a where
         f &&& g = arr (\b -> (b,b)) >>> f *** g
 
 {-# RULES
-"identity"
-                arr id = id
 "compose/arr"   forall f g .
                 (arr f) . (arr g) = arr (f . g)
 "first/arr"     forall f .
@@ -221,9 +214,9 @@ class Arrow a => ArrowChoice a where
 "fanin/arr"     forall f g .
                 arr f ||| arr g = arr (f ||| g)
 "compose/left"  forall f g .
-                left f >>> left g = left (f >>> g)
+                left f . left g = left (f . g)
 "compose/right" forall f g .
-                right f >>> right g = right (f >>> g)
+                right f . right g = right (f . g)
  #-}
 
 instance ArrowChoice (->) where