/**
* Copyright (c) 1999-2014, Ecole des Mines de Nantes
* All rights reserved.
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* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of the Ecole des Mines de Nantes 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 THE REGENTS AND CONTRIBUTORS ``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
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package solver.constraints.reification;
import memory.structure.Operation;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import solver.constraints.Constraint;
import solver.constraints.Propagator;
import solver.constraints.PropagatorPriority;
import solver.exception.ContradictionException;
import solver.variables.Variable;
import util.ESat;
/**
* A specific propagator which posts constraint on condition.
* <br/>
* The user gives the condition, then <br/>
* if the condition returns ESat.TRUE, then posts temporarily the first propagator,<br/>
* if the condition returns Esat.FALSE, then it posts temporarily the second propagator,<br/>
* Otherwise wait for the condition to be fully (un)satisfied.
*
* @author Charles Prud'homme
* @since 06/02/2014
*/
public abstract class PropConditionnal extends Propagator<Variable> {
private static Logger LOGGER = LoggerFactory.getLogger("propagator");
Constraint[] condTrue;
Constraint[] condFalse;
/**
* @param vars2observe set of variables to observe, their modifications triggers the condition checking
* @param condTrue the constraint to post if the condition is satisfied
* @param condFalse the constraint to post if the condition is not satisfied
*/
public PropConditionnal(Variable[] vars2observe, Constraint[] condTrue, Constraint[] condFalse) {
super(vars2observe, PropagatorPriority.VERY_SLOW, false);
this.condTrue = condTrue.clone();
this.condFalse = condFalse.clone();
}
@Override
public void propagate(int evtmask) throws ContradictionException {
ESat condition = checkCondition();
if (condition == ESat.TRUE) {
setPassive();
for (Constraint cstr : condTrue) {
postTemp(cstr);
}
} else if (condition == ESat.FALSE) {
setPassive();
for (Constraint cstr : condFalse) {
postTemp(cstr);
}
}
}
private void postTemp(final Constraint c) throws ContradictionException {
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("post " + c.toString());
}
solver.postTemp(c);
// the constraint has been added during the resolution.
// it should be removed on backtrack -> create a new undo operation
solver.getEnvironment().save(new Operation() {
@Override
public void undo() {
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("unpost " + c.toString());
}
solver.unpost(c);
}
});
}
@Override
public ESat isEntailed() {
return ESat.TRUE;
}
/**
* Check a specific condition.<br/>
* If the condition returns ESat.TRUE, then posts temporarily the first propagator,<br/>
* If the condition returns Esat.FALSE, then it posts temporarily the second propagator,<br/>
* Otherwise wait for the condition to be fully (un)satisfied.
*
* @return Esat
*/
public abstract ESat checkCondition();
}