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/*******************************************************************************
* Copyright (c) 2009 Cloudsmith Inc. and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Cloudsmith Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.p2.ql;
import java.util.Iterator;
import org.eclipse.equinox.p2.metadata.expression.IEvaluationContext;
import org.eclipse.equinox.p2.metadata.expression.IExpression;
/**
* This is an expression that will need access to the global variable
* <code>everything</code>.
*/
public interface IContextExpression<T> extends IExpression {
/**
* <p>Creates a new context to be passed to a subsequent evaluation. The context
* will have the variable 'everything' set to an expression that represents
* the <code>everything</code> iterator filtered for instances of <code>elementClass</code>.</p>
* <p>The values of the iterator will be copied if necessary (when everything is referenced
* more then once).</p>
* @param everything The iterator that represents all queried material.
* @return A new evaluation context.
*/
IEvaluationContext createContext(Iterator<T> everything);
/**
* <p>Creates a new context to be passed to a subsequent evaluation. The context
* will have the variable 'everything' set to an expression that represents
* the <code>everything</code> iterator filtered for instances of <code>elementClass</code>.</p>
* <p>The values of the iterator will be copied if necessary (when everything is referenced
* more then once).</p>
* @param everything The iterator that represents all queried material.
* @param translations A translation support object to be assigned to the variable 'translations'
* @return A new evaluation context.
*/
IEvaluationContext createContext(Iterator<T> everything, ITranslationSupport translations);
/**
* Returns the element class
* @return The element class
*/
Class<T> getElementClass();
/**
* Returns the parameters that this context expression was created with.
* @return An array of parameters, possibly empty but never <code>null</code>.
*/
Object[] getParameters();
/**
* Evaluate the expression and return the expected collection result as an iterator
* @param context The evaluation context
* @return The result of the evaluation.
*/
Iterator<T> iterator(IEvaluationContext context);
}
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