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/*******************************************************************************
* Copyright (c) 2010-2013, Zoltan Ujhelyi, Akos Horvath, Istvan Rath and Daniel Varro
* Copyright (c) 2023 The Refinery Authors <https://refinery.tools/>
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.viatra.runtime.localsearch.operations;
import tools.refinery.viatra.runtime.localsearch.MatchingFrame;
import tools.refinery.viatra.runtime.localsearch.matcher.ISearchContext;
import tools.refinery.viatra.runtime.localsearch.operations.ISearchOperation.ISearchOperationExecutor;
import java.util.Iterator;
/**
* An operation that can be used to enumerate all possible values for a single position based on a constraint
* @author Zoltan Ujhelyi, Akos Horvath
* @noextend This class is not intended to be subclassed by clients.
* @since 2.0
*/
public abstract class ExtendOperationExecutor<T> implements ISearchOperationExecutor {
private Iterator<? extends T> it;
/**
* Returns an iterator with the possible options from the current state
* @since 2.0
*/
protected abstract Iterator<? extends T> getIterator(MatchingFrame frame, ISearchContext context);
/**
* Updates the frame with the next element of the iterator. Called during {@link #execute(MatchingFrame, ISearchContext)}.
*
* @return true if the update is successful or false otherwise; in case of false is returned, the next element should be taken from the iterator.
* @since 2.0
*/
protected abstract boolean fillInValue(T newValue, MatchingFrame frame, ISearchContext context);
/**
* Restores the frame to the state before {@link #fillInValue(Object, MatchingFrame, ISearchContext)}. Called during
* {@link #onBacktrack(MatchingFrame, ISearchContext)}.
*
* @since 2.0
*/
protected abstract void cleanup(MatchingFrame frame, ISearchContext context);
@Override
public void onInitialize(MatchingFrame frame, ISearchContext context) {
it = getIterator(frame, context);
}
@Override
public void onBacktrack(MatchingFrame frame, ISearchContext context) {
it = null;
}
/**
* Fixed version that handles failed unification of variables correctly.
* @param frame The matching frame to extend.
* @param context The search context.
* @return {@code true} if an extension was found, {@code false} otherwise.
*/
@Override
public boolean execute(MatchingFrame frame, ISearchContext context) {
while (it.hasNext()) {
var newValue = it.next();
if (fillInValue(newValue, frame, context)) {
return true;
}
}
return false;
}
}
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