From ac950d8bd790a4e5d5581006e6ead20d03068c91 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Wed, 26 Jan 2011 17:24:55 -0800
Subject: [PATCH] sets: improve stack effect for "combine".

---
 core/sets/sets.factor | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/sets/sets.factor b/core/sets/sets.factor
index 06f6e04655..5dcee675f9 100644
--- a/core/sets/sets.factor
+++ b/core/sets/sets.factor
@@ -109,7 +109,7 @@ M: sequence null?
 M: sequence cardinality
     length ;
 
-: combine ( sets -- set )
+: combine ( sets -- set/f )
     [ f ]
     [ [ [ members ] map concat ] [ first ] bi set-like ]
     if-empty ;