From 14bae4cb7e75dc7d4c01ebbcb167c029012139a9 Mon Sep 17 00:00:00 2001
From: Vitor Santos Costa <vsc@dcc.fc.up.pt>
Date: Sun, 8 May 2011 23:11:40 +0100
Subject: [PATCH] avoid choice-point in ord-union.

---
 library/ordsets.yap | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/ordsets.yap b/library/ordsets.yap
index 3dee38aa7..b6a780bcb 100644
--- a/library/ordsets.yap
+++ b/library/ordsets.yap
@@ -274,8 +274,8 @@ ord_symdiff(>, Head1, Tail1, Head2, Tail2, [Head2|Difference]) :-
 %   is true when Union is the union of Set1 and Set2.  Note that when
 %   something occurs in both sets, we want to retain only one copy.
 
-ord_union(Set1, [], Set1) :- !.
-ord_union([], Set2, Set2) :- !.
+ord_union([S|Set1], [], [S|Set1]).
+ord_union([], Set2, Set2).
 ord_union([Head1|Tail1], [Head2|Tail2], Union) :-
 	compare(Order, Head1, Head2),
 	ord_union(Order, Head1, Tail1, Head2, Tail2, Union).