SetView::variable(void) works for me!
Ok, good. The only problem is that you can't get the pointer back to
something you can use... You'd have to add another constructor to
SetView that takes a SetVarImp*.
// this function could be called something like
// LubRanges_from_SetVar
{
...
SetVar* set;
SetView view(*set);
return new LubRanges ranges(view); // (this would not work I
suppose....)
}
This will work!
:) And this one two!
But concerning the SetView, when the function returns I think the
destructor is called and then it is deallocated from the stack,
right? This does no harm since the LubRanges is working on the
underlying implementation.
SetView and SetVar (and all other views and vars) are nothing but
wrappers around a single pointer. This pointer is never affected by
any allocation or deallocation of a var or view. That's why nothing
goes wrong here. And the pointer is normally kept internal because
you cannot do anything useful with it - except maybe for storing it
somewhere.
But in general, shouldn't I be able to create an Object like
SetView, or e.g
Gecode::Int::OffsetView with a function and return it to Lisp
directly?
I imagine the case, where I could pass an Int::OffsetView to a
propagator, freeing me from the need to create a new IntVar to only
represent a constant addition of 1 for example.
Maybe I am even not supposed to do something like that?
No, you're not. You can't call a propagator with an OffsetView
anyway! The posting interface for propagators only accepts SetVars
(or IntVars or BoolVars). The offset is not represented in the actual
variable data structures, only in the view wrapper. This is an
internal mechanism for getting more propagators out of a single
implementation (we wrote a paper about this, if you're interested in
what can be done with views).
Cheers,
Guido
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