001/**
002 *   GRANITE DATA SERVICES
003 *   Copyright (C) 2006-2013 GRANITE DATA SERVICES S.A.S.
004 *
005 *   This file is part of the Granite Data Services Platform.
006 *
007 *   Granite Data Services is free software; you can redistribute it and/or
008 *   modify it under the terms of the GNU Lesser General Public
009 *   License as published by the Free Software Foundation; either
010 *   version 2.1 of the License, or (at your option) any later version.
011 *
012 *   Granite Data Services is distributed in the hope that it will be useful,
013 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
014 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
015 *   General Public License for more details.
016 *
017 *   You should have received a copy of the GNU Lesser General Public
018 *   License along with this library; if not, write to the Free Software
019 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
020 *   USA, or see <http://www.gnu.org/licenses/>.
021 */
022package org.granite.gravity.selector;
023
024/**
025 * An expression which performs an operation on two expression values.
026 *
027 * @version $Revision: 1.2 $
028 */
029abstract public class BinaryExpression implements Expression {
030    protected Expression left;
031    protected Expression right;
032
033    public BinaryExpression(Expression left, Expression right) {
034        this.left = left;
035        this.right = right;
036    }
037
038    public Expression getLeft() {
039        return left;
040    }
041
042    public Expression getRight() {
043        return right;
044    }
045
046
047    /**
048     * @see java.lang.Object#toString()
049     */
050    @Override
051    public String toString() {
052        return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
053    }
054
055    /**
056     * TODO: more efficient hashCode()
057     *
058     * @see java.lang.Object#hashCode()
059     */
060    @Override
061    public int hashCode() {
062        return toString().hashCode();
063    }
064
065    /**
066     * TODO: more efficient hashCode()
067     *
068     * @see java.lang.Object#equals(java.lang.Object)
069     */
070    @Override
071    public boolean equals(Object o) {
072
073        if (o == null || !this.getClass().equals(o.getClass())) {
074            return false;
075        }
076        return toString().equals(o.toString());
077
078    }
079
080    /**
081     * Returns the symbol that represents this binary expression.  For example, addition is
082     * represented by "+"
083     *
084     * @return the symbol
085     */
086    abstract public String getExpressionSymbol();
087
088    /**
089     * @param expression
090     */
091    public void setRight(Expression expression) {
092        right = expression;
093    }
094
095    /**
096     * @param expression
097     */
098    public void setLeft(Expression expression) {
099        left = expression;
100    }
101
102}