question concerning the alldifferent predicate

Hello,
 
I have a question concerning the alldifferent predicate.
 
The example below compiles well in eclipse, but the query "foo( Vert,
Hor )." results in an "abort" with the error message:
 
out of range in ic_excl(ic(Hor{-1.0Inf .. 1.0Inf}, integer, -1.0Inf,
1.0Inf, undefined, [], [], [], []), 3)
 
If I replace the alldifferent predicate with the #\= operator,
everything works fine. In fact, the example below is just the iolated
problem, my actual data contain much more facts and foo is more complex,
in particular, it takes more arguments which have to be pairwse
disjoint. Of course, I could realize pairwise disjointness with a
conjunction of #\= operators, but this is not elegant. 
Is there a better solution for this problem? And I wonder about the
reason why alldifferent does not work here.
 
Thanks in advance
 
Cornelius Hagen
 

***** Example **********************

:- use_module(library(ic)).
 
line( 3, 0.9, 0.0, 1.0 ).
line( 1, 0.9, 0.0, 0.0 ).
line( 9, 0.6, -1.0, 0.0 ).
line( 7, 0.9, 0.0, 0.0 ).
line( 5, 0.9, 0.0, 1.0 ).
 
 
foo( Vert, Hor ) :-
 
alldifferent( [ Vert, Hor] ),
% Vert #\= Hor,
 
line( Vert, ObjConfVert, Vertx, Vertytop ),
line( Hor, ObjConfHor, Hory, Horxr ).

 
-------------------------------------------------
 
Dipl. Math. Cornelius Hagen
 
Lehrstuhl für Angewandte Informatik in den Kultur, Geschichts- und
Geowissenschaften
 
Feldkirchenstr. 21
D-96045 Bamberg
 
Tel: + 951 / 863-2843
 
E-Mail: cornelius.hagen@wiai.uni-bamberg.de
Homepage: http://www.uni-bamberg.de/~ba7ag99/cornelius_hagen.htm