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/*******************************************************************************
 * Copyright (c) 2011, 2014 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation
 *
 ******************************************************************************/
package org.eclipse.persistence.jpa.jpql.tools.model.query;

import org.eclipse.persistence.jpa.jpql.parser.ConditionalExpressionBNF;
import org.eclipse.persistence.jpa.jpql.parser.ConditionalTermBNF;
import org.eclipse.persistence.jpa.jpql.parser.OrExpression;
import static org.eclipse.persistence.jpa.jpql.parser.Expression.*;

/**
 * The OR logical operator chains multiple criteria together. A valid operand
 * of an OR operator must be one of: TRUE,
 * FALSE, and NULL. The OR operator has
 * a lower precedence than the AND operator.
 * 
 * NULL represents unknown. Therefore, if one operand is NULL
 * and the other operand is TRUE the result is TRUE, because
 * one TRUE operand is sufficient for a TRUE result. If one
 * operand is NULL and the other operand is either FALSE or
 * NULL, the result is NULL (unknown).
 * 

 * The following table shows how the OR operator is evaluated based on its two operands:
 *
 * 
 * 
 * 
 * 
 * 
 * TRUE FALSE NULL
TRUE TRUE TRUE TRUE
FALSE TRUE FALSE NULL
NULL TRUE NULL NULL
 *
 * BNF: conditional_expression ::= conditional_expression OR conditional_term
 *
 * @see OrExpression
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public class OrExpressionStateObject extends LogicalExpressionStateObject {

	/**
	 * Creates a new OrExpressionStateObject.
	 *
	 * @param parent The parent of this state object, which cannot be null
	 * @exception NullPointerException The given parent cannot be null
	 */
	public OrExpressionStateObject(StateObject parent) {
		super(parent);
	}

	/**
	 * Creates a new OrExpressionStateObject.
	 *
	 * @param parent The parent of this state object, which cannot be null
	 * @param leftStateObject The {@link StateObject} representing the left expression
	 * @param rightStateObject The {@link StateObject} representing the right expression
	 * @exception NullPointerException The given parent cannot be null
	 */
	public OrExpressionStateObject(StateObject parent,
	                               StateObject leftStateObject,
	                               StateObject rightStateObject) {

		super(parent, leftStateObject, rightStateObject);
	}

	/**
	 * Creates a new OrExpressionStateObject.
	 *
	 * @param parent The parent of this state object, which cannot be null
	 * @param leftJpqlFragment The string representation of the left expression to parse and to
	 * convert into a {@link StateObject}
	 * @param rightJpqlFragment The string representation of the right expression to parse and to
	 * convert into a {@link StateObject}
	 * @exception NullPointerException The given parent cannot be null
	 */
	public OrExpressionStateObject(StateObject parent,
	                               String leftJpqlFragment,
	                               String rightJpqlFragment) {

		super(parent, leftJpqlFragment, rightJpqlFragment);
	}

	/**
	 * {@inheritDoc}
	 */
	public void accept(StateObjectVisitor visitor) {
		visitor.visit(this);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public OrExpression getExpression() {
		return (OrExpression) super.getExpression();
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String getIdentifier() {
		return OR;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	protected String getLeftQueryBNFId() {
		return ConditionalExpressionBNF.ID;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	protected String getRightQueryBNFId() {
		return ConditionalTermBNF.ID;
	}

	/**
	 * Keeps a reference of the {@link OrExpression parsed object} object, which should only be
	 * done when this object is instantiated during the conversion of a parsed JPQL query into
	 * {@link StateObject StateObjects}.
	 *
	 * @param expression The {@link OrExpression parsed object} representing a logical
	 * OR expression
	 */
	public void setExpression(OrExpression expression) {
		super.setExpression(expression);
	}
}
	TRUE	FALSE	NULL
TRUE	TRUE	TRUE	TRUE
FALSE	TRUE	FALSE	NULL
NULL	TRUE	NULL	NULL