[gecode-users] Getting just assigned variable from ViewArray in a propagator

[Yunus Acikoz]

Hi everyone,

I have a tunneling constraint propagator that has 4 ViewArrays and
scheduled to run on their assignment events:

    Gecode::ViewArray<Gecode::Int::IntView> successors_;
  Gecode::ViewArray<Gecode::Int::IntView> predecessors_;
  Gecode::ViewArray<Gecode::Int::IntView> vehicles_;
  Gecode::ViewArray<Gecode::Int::BoolView> cancels_;

  successors_.subscribe(home, *this, Gecode::Int::PC_INT_VAL);
  predecessors_.subscribe(home, *this, Gecode::Int::PC_INT_VAL);
  vehicles_.subscribe(home, *this, Gecode::Int::PC_INT_VAL);

I want to post additional constraints whenever a value gets fixed over
those arrays.

for (int i = 0; i < successors_.size(); ++i) {
    if (vehicles_[i].assigned()) {
        int val = vehicles_[i].val();
        // post constraint...
        // eg.
        Gecode::element(home, vehicles_, successors_[i], val);
    }
    if (successors_[i].assigned()) {
        int val = successors_[i].val();
        // post another constraint ...
    }
}

For example assume that we first assign the vehicle[2] to some value and
propagate accordingly.
Then if we assign vehicle[7] how can we prevent doing same action for
vehicle[2].

Does it post the same constraints for all the previously assigned
variables, again and again.... ?

Is there a way to get the recently assigned variable that cause thıs
propagator to run?

Cheers,
Yunus
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