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Open-source constraint solver.
There is a newer version: 4.10.17
/*
 * This file is part of choco-solver, http://choco-solver.org/
 *
 * Copyright (c) 2022, IMT Atlantique. All rights reserved.
 *
 * Licensed under the BSD 4-clause license.
 *
 * See LICENSE file in the project root for full license information.
 */
package org.chocosolver.solver.variables.view.set;

import org.chocosolver.solver.ICause;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.SetVar;
import org.chocosolver.solver.variables.delta.ISetDelta;
import org.chocosolver.solver.variables.delta.ISetDeltaMonitor;
import org.chocosolver.solver.variables.events.IEventType;
import org.chocosolver.solver.variables.events.SetEventType;
import org.chocosolver.solver.variables.view.SetView;
import org.chocosolver.solver.variables.view.delta.SetViewOnSetsDeltaMonitor;
import org.chocosolver.util.objects.setDataStructures.ISet;
import org.chocosolver.util.objects.setDataStructures.dynamic.SetDifference;
import org.chocosolver.util.procedure.IntProcedure;

/**
 * Set view representing the set difference of two set variables: z = x \ y.
 *
 * @author Dimitri Justeau-Allaire
 * @since 29/03/2021
 */
public class SetDifferenceView extends SetView {

    protected SetDifference lb;
    protected SetDifference ub;

    protected SetVar x, y;

    /**
     * Create a set difference view z = x \ y
     *
     * @param name      name of the variable
     * @param x A set variable.
     * @param y A set variable.
     */
    public SetDifferenceView(String name, SetVar x, SetVar y) {
        super(name, x, y);
        this.x = x;
        this.y = y;
        this.lb = new SetDifference(getModel(), x.getLB(), y.getLB());
        this.ub = new SetDifference(getModel(), x.getUB(), y.getLB());
    }

    @Override
    public ISet getLB() {
        return lb;
    }

    @Override
    public ISet getUB() {
        return ub;
    }

    @Override
    public boolean instantiateTo(int[] value, ICause cause) throws ContradictionException {
        return false;
    }

    @Override
    public boolean isInstantiated() {
        return getLB().size() == getUB().size();
    }

    @Override
    public void notify(IEventType event, int variableIdx) throws ContradictionException {
        notifyPropagators(event, this);
    }

    @Override
    protected boolean doRemoveSetElement(int element) throws ContradictionException {
        // Remove element from x iff:
        //      element in x.getUB() && element not in y.getUB()
        if (x.getUB().contains(element) && !y.getUB().contains(element)) {
            return x.remove(element, this);
        }
        // Force element to y iff:
        //      element in x.getLB() && element in y.getUB()
        if (x.getLB().contains(element) && y.getUB().contains(element)) {
            return y.force(element, this);
        }
        return false;
    }

    @Override
    protected boolean doForceSetElement(int element) throws ContradictionException {
        // Force element to x and remove it from y
        return x.force(element, this) | y.remove(element, this);
    }

    @Override
    public ISetDelta getDelta() {
        throw new UnsupportedOperationException("SetDifferenceView does not support getDelta()");
    }

    @Override
    public ISetDeltaMonitor monitorDelta(ICause propagator) {
        return new SetViewOnSetsDeltaMonitor(x.monitorDelta(propagator), y.monitorDelta(propagator)) {
            @Override
            public void forEach(IntProcedure proc, SetEventType evt) throws ContradictionException {
                fillValues();
                if (evt == SetEventType.ADD_TO_KER) {
                    for (int v : addedValues[0]) {
                        if (lb.contains(v)) {
                            proc.execute(v);
                        }
                    }
                    for (int v : removedValues[1]) {
                        if (lb.contains(v)) {
                            proc.execute(v);
                        }
                    }
                } else if (evt == SetEventType.REMOVE_FROM_ENVELOPE) {
                    for (int v : removedValues[0]) {
                        if (!y.getLB().contains(v) && !removedValues[1].contains(v)) {
                            proc.execute(v);
                        }
                    }
                    for (int v : addedValues[1]) {
                        if (x.getUB().contains(v) && !addedValues[0].contains(v)) {
                            proc.execute(v);
                        }
                    }
                }
            }
        };
    }
}