Fix a bug reported by Leon Smith:

http://splonderzoek.blogspot.com/2009/02/incremental-fold-design-pattern.html?showComment=1238634360000#c4648170459155928968
spl · Apr 2, 2009 · ca2f7ee · ca2f7ee
1 parent 9b6c144
commit ca2f7ee
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/IncrementalTreeFold.lhs b/IncrementalTreeFold.lhs
@@ -142,7 +142,7 @@ I use the datatype <code>Alg</code> here to contain the <a href="http://www.alph
 <pre>
 
 > filter :: (a -> Bool) -> Tree a -> [a]
-> filter f = fold (Alg [] (\x lr rr -> if f x then [x] else [] ++ lr ++ rr))
+> filter f = fold (Alg [] (\x lr rr -> (if f x then [x] else []) ++ lr ++ rr))
 
 > ord :: Tree Char -> Tree Int
 > ord  = fold (Alg Tip (\x lt rt -> Bin (Char.ord x) lt rt))