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/**
 *   GRANITE DATA SERVICES
 *   Copyright (C) 2006-2014 GRANITE DATA SERVICES S.A.S.
 *
 *   This file is part of the Granite Data Services Platform.
 *
 *   Granite Data Services is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   Granite Data Services is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
 *   General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 *   USA, or see .
 */
package org.granite.gravity.selector;

/**
 * An expression which performs an operation on two expression values.
 *
 * @version $Revision: 1.2 $
 */
abstract public class BinaryExpression implements Expression {
    protected Expression left;
    protected Expression right;

    public BinaryExpression(Expression left, Expression right) {
        this.left = left;
        this.right = right;
    }

    public Expression getLeft() {
        return left;
    }

    public Expression getRight() {
        return right;
    }


    /**
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object o) {

        if (o == null || !this.getClass().equals(o.getClass())) {
            return false;
        }
        return toString().equals(o.toString());

    }

    /**
     * Returns the symbol that represents this binary expression.  For example, addition is
     * represented by "+"
     *
     * @return the symbol
     */
    abstract public String getExpressionSymbol();

    /**
     * @param expression
     */
    public void setRight(Expression expression) {
        right = expression;
    }

    /**
     * @param expression
     */
    public void setLeft(Expression expression) {
        left = expression;
    }

}