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OpenL Constraint Programming engine

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package org.openl.ie.constrainer.impl;

import org.openl.ie.constrainer.*;

///////////////////////////////////////////////////////////////////////////////
/*
 * Copyright Exigen Group 1998, 1999, 2000
 * 320 Amboy Ave., Metuchen, NJ, 08840, USA, www.exigengroup.com
 *
 * The copyright to the computer program(s) herein
 * is the property of Exigen Group, USA. All rights reserved.
 * The program(s) may be used and/or copied only with
 * the written permission of Exigen Group
 * or in accordance with the terms and conditions
 * stipulated in the agreement/contract under which
 * the program(s) have been supplied.
 */
///////////////////////////////////////////////////////////////////////////////
/**
 * An implementation of the constraint: IntExp == value.
 */
public final class ConstraintExpEqualsValue extends ConstraintImpl {
    // PRIVATE MEMBERS
    private final IntExp _exp;
    private final int _value;
    private Constraint _opposite;

    public ConstraintExpEqualsValue(IntExp exp, int value) {
        super(exp.constrainer());

        if (constrainer().showInternalNames()) {
            _name = "(" + exp.name() + "==" + value + ")";
        }

        _exp = exp;
        _value = value;
    }

    @Override
    public Goal execute() throws Failure {
        class ObserverEqualValue extends Observer {
            @Override
            public Object master() {
                return ConstraintExpEqualsValue.this;
            }

            @Override
            public int subscriberMask() {
                return EventOfInterest.VALUE | EventOfInterest.MIN | EventOfInterest.MAX;
            }

            @Override
            public String toString() {
                return "ObserverEqualValue";
            }

            @Override
            public void update(Subject exp, EventOfInterest interest) throws Failure {
                // Debug.on();Debug.print("ObserverEqualValue:
                // "+interest);Debug.off();
                IntEvent event = (IntEvent) interest;
                if (event.isValueEvent() && event.min() != _value || event.isMaxEvent() && event.max() < _value || event
                    .isMinEvent() && event.min() > _value) {
                    exp.constrainer().fail("from ObserverEqualValue");
                }
                _exp.setValue(_value);
            }

        } // ~ ObserverEqualValue

        _exp.setValue(_value); // may fail
        _exp.attachObserver(new ObserverEqualValue());
        return null;
    }

    @Override
    public String toString() {
        return _exp + "=" + _value;
    }

} // ~ ConstraintExpEqualsValue