Changes between Version 11 and Version 12 of ViewPatterns

Timestamp:

01/24/07 05:47:00 (6 years ago)

Author:

malcolm.wallace@…

Comment:

The "sets as lists" example had an incorrect implementation of insert.

ViewPatterns

@@ -257 +257 @@
   has :: Eq a => a -> Set a -> Maybe (Set a)
   has x (S xs) | x `elem` xs = Just (xs \\ x)
-               | otherwise   = Nothing
+                   | otherwise   = Nothing
   
   delete :: a -> Set a -> Set a
@@ -265 +265 @@
   insert :: a -> Set a -> Set a
   insert x s@(has x -> _) = s
-  insert x s              = s
+  insert x (S xs)         = S (x:xs)
 }}}
 Notice that in the left-hand side `delete x (has x -> s)`, the first `x` is a binding occurrence,