@Override
public void explain(Deduction d, Explanation e) {
e.add(solver.getExplainer().getPropagatorActivation(this));
e.add(aCause);
// the current deduction is due to the current domain of the involved variables
Variable var = d.getVar();
if (var.equals(x)) {
// a deduction has been made on x ; this is related to y only
y.explain(VariableState.LB, e);
} else if (var.equals(y)) {
x.explain(VariableState.UB, e);
} else {
super.explain(d, e);
}
}