[project @ 2004-09-06 17:20:02 by ross]

[ghc-base.git] / Control / Arrow.hs

diff --git a/Control/Arrow.hs b/Control/Arrow.hs
index f6ee713..316ef06 100644 (file)
--- a/Control/Arrow.hs
+++ b/Control/Arrow.hs
@@ -93,6 +93,23 @@ class Arrow a where
        (&&&) :: a b c -> a b c' -> a b (c,c')
        f &&& g = arr (\b -> (b,b)) >>> f *** g
 
+{-# RULES
+"compose/arr"  forall f g .
+               arr f >>> arr g = arr (f >>> g)
+"first/arr"    forall f .
+               first (arr f) = arr (first f)
+"second/arr"   forall f .
+               second (arr f) = arr (second f)
+"product/arr"  forall f g .
+               arr f *** arr g = arr (f *** g)
+"fanout/arr"   forall f g .
+               arr f &&& arr g = arr (f &&& g)
+"compose/first"        forall f g .
+               first f >>> first g = first (f >>> g)
+"compose/second" forall f g .
+               second f >>> second g = second (f >>> g)
+ #-}
+
 -- Ordinary functions are arrows.
 
 instance Arrow (->) where
@@ -175,6 +192,21 @@ class Arrow a => ArrowChoice a where
                        where   untag (Left x) = x
                                untag (Right y) = y
 
+{-# RULES
+"left/arr"     forall f .
+               left (arr f) = arr (left f)
+"right/arr"    forall f .
+               right (arr f) = arr (right f)
+"sum/arr"      forall f g .
+               arr f +++ arr g = arr (f +++ g)
+"fanin/arr"    forall f g .
+               arr f ||| arr g = arr (f ||| g)
+"compose/left" forall f g .
+               left f >>> left g = left (f >>> g)
+"compose/right"        forall f g .
+               right f >>> right g = right (f >>> g)
+ #-}
+
 instance ArrowChoice (->) where
        left f = f +++ id
        right f = id +++ f