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/*******************************************************************************
 * Copyright (c) 2006, 2013 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.parser;

/**
 * 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
 *
 * @version 2.4.2
 * @since 2.3
 * @author Pascal Filion
 */
public final class OrExpression extends LogicalExpression {

	/**
	 * Creates a new OrExpression.
	 *
	 * @param parent The parent of this expression
	 */
	public OrExpression(AbstractExpression parent) {
		super(parent, OR);
	}

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

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String leftExpressionBNF() {
		return ConditionalExpressionBNF.ID;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String rightExpressionBNF() {
		return ConditionalTermBNF.ID;
	}
}

	TRUE	FALSE	NULL
TRUE	TRUE	TRUE	TRUE
FALSE	TRUE	FALSE	NULL
NULL	TRUE	NULL	NULL