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OpenL Constraint Programming engine

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package org.openl.ie.constrainer.impl;

import org.openl.ie.constrainer.*;

/**
 * An implementation of the expression: (IntExp < IntExp + offset).
 */
public class IntBoolExpLessExp extends IntBoolExpForSubject {
    final class ObserverMinMax extends Observer {
        @Override
        public Object master() {
            return IntBoolExpLessExp.this;
        }

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

        @Override
        public void update(Subject subject, EventOfInterest interest) throws Failure {
            setDomainMinMax();
        }

    } // ~ObserverMinMax

    protected final IntExp _left;
    protected final IntExp _right;
    protected final int _offset;

    private final Observer _observer;

    public IntBoolExpLessExp(IntExp left, IntExp right) {
        this(left, right, 0);
    }

    public IntBoolExpLessExp(IntExp left, IntExp right, int offset) {
        super(left.constrainer());

        _left = left;
        _right = right;
        _offset = offset;

        if (constrainer().showInternalNames()) {
            _name = "(" + left.name() + "<" + right.name() + "+" + offset + ")";
        }

        setDomainMinMaxSafe();

        _observer = new ObserverMinMax();
        _left.attachObserver(_observer);
        _right.attachObserver(_observer);
    }

    @Override
    public boolean isLinear() {
        return _left.isLinear() && _right.isLinear();
    }

    @Override
    protected boolean isSubjectFalse() {
        return _left.min() >= _right.max() + _offset;
    }

    @Override
    protected boolean isSubjectTrue() {
        return _left.max() < _right.min() + _offset;
    }

    @Override
    protected void setSubjectFalse() throws Failure {
        // left >= right + offset
        _left.setMin(_right.min() + _offset);
        _right.setMax(_left.max() - _offset);
    }

    @Override
    protected void setSubjectTrue() throws Failure {
        // left < right + offset
        _left.setMax(_right.max() + _offset - 1);
        _right.setMin(_left.min() - _offset + 1);
    }

} // ~IntBoolExpLessExp