FD and Multiplication

Hi,

Any reason that the following fails:

	?- (Y-5)*(X-6) #= 0.
         No

Best Regards

P.S.: On the other the following works:

    ?- (X-5)*(X-6) #= 0, fd_labeling(X).
    X = 5 ? ;
    X = 6

But I didn't figure out how to list the
actual constraint store, and also I didn't
figure out how to get heuristic information
that is for example used in labeling, such
as the weight used in "most constraints".

Listing the constraint store and/or
heuristic information would also help
debugging the query that fails.