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Open-source constraint solver.
There is a newer version: 4.10.16
/**
 * Copyright (c) 2016, Ecole des Mines de Nantes
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the .
 * 4. Neither the name of the  nor the
 *    names of its contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY  ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL  BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.chocosolver.solver.constraints.set;

import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.SetVar;
import org.chocosolver.util.ESat;

/**
 * Restricts the set var not to be empty
 *
 * @author Jean-Guillaume Fages
 */
public class PropNotEmpty extends Propagator {

	//***********************************************************************************
	// CONSTRUCTORS
	//***********************************************************************************

	public PropNotEmpty(SetVar set) {
		super(new SetVar[]{set}, PropagatorPriority.UNARY, false);
	}

	//***********************************************************************************
	// METHODS
	//***********************************************************************************

	@Override
	public void propagate(int evtmask) throws ContradictionException {
		int e = vars[0].getUB().size();
		if(e==0){
			fails(); // TODO: could be more precise, for explanation purpose
		}else if(e==1){
			vars[0].force(vars[0].getUB().iterator().next(), this);
		}
		if(vars[0].getLB().size()>0){
			setPassive();
		}
	}

	@Override
	public ESat isEntailed() {
		if(vars[0].getUB().size()==0){
			return ESat.FALSE;
		}
		if(vars[0].getLB().size()>0){
			return ESat.TRUE;
		}
		return ESat.UNDEFINED;
	}

}