Hi!
I'm not sure I understand your syntax. Is this C++, do you e.g. mean
Gecode::me_failed? Assuming that this is the case, let's have a look
at your questions.
Debdeep Banerjee wrote:
> hi,
> I have some questions about reducing domain of a variable. Say I
> have a
> IntVar x and its domain is IntSet {1,2,5,6,-2}
> q1. if I want say x != 2 then I use the following code
> IntView v(x)
> Gecode.me_failed( v.nq( home, 2 ) ) ==> this should return
> true/1
> Is this correct ?
No, it should return false. The semantics of nq is the following (in
pseudo code):
nq(int i):
domain := domain - {i}
if domain is empty return false else return true
The domain contains 2, and after you say v.nq(home,2), it does not
contain 2 any more, but there are other values left, so the operation
does not result in failure.
> q2. Say x is already assigned to 5, ie
> IntView v(x) and v.assigned() == true.
> What will happen if I try to do the following
> Gecode.me_failed( v.nq( home, 2 ) ) == > what should this code
> return 0 or 1 ??
If you remove a value from a domain that isn't in the domain, the
operation does not fail, because the resulting domain is not empty.
> q3. Say I want to say x != 9 ( 9 is not in the domain of x)
> IntView v(x)
> Gecode.me_failed( v.nq( home, 9 ) ==> what this will return ???
> Does this depends on whether x is already assigned or not ??
Same as above, if 9 is not in the domain, the operation does not
fail. This has nothing to do with whether x is assigned or not.
Finally, in what context are you using these operations? The fact
that you wrote IntView v(x) made me think you might be trying this in
a model. The operations really should only be used in propagators and
branchings, definitely not in a model! Use rel/dom constraint posting
functions instead.
Cheers,
Guido
_______________________________________________
Gecode users mailing list
[EMAIL PROTECTED]
https://www.gecode.org/mailman/listinfo/gecode-users
