[Oz] Filtering of values of constraint variables

[Benko Tamas]

Dear Denys,

> > In Prolog it looks like this:
> > 
> > % Try to filter out value V from variable X.
> > filter(X, V) :-
> >         (   \+ X = V -> X #\= V
> >         ;   true
> >         ).
> 
> It seems to me that, for finite domain and finite set variables, what
> you outline above is pointless since X=V fails precisely when V is no
> longer a value in the domain of X.

No, (because of the incompleteness of the FD solver) X=V can fail even if
the domain of X contains V.  It happens quite often that none of the
propagators posted on X can infer that V is inconsistent, but as soon as X
is instantiated to V, they detect the inconsistency.

I haven't really digested your whole mail yet, it might (and probably will)
help me.  Thank you.

--Tamas
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