/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.jxpath.ri.compiler;
import org.apache.commons.jxpath.ri.EvalContext;
/**
* The common subclass for tree elements representing core operations like "+",
* "- ", "*" etc.
*
* @author Dmitri Plotnikov
* @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
*/
public abstract class CoreOperation extends Operation {
/** or precedence */
protected static final int OR_PRECEDENCE = 0;
/** and precedence */
protected static final int AND_PRECEDENCE = 1;
/** compare precedence */
protected static final int COMPARE_PRECEDENCE = 2;
/** relational expression precedence */
protected static final int RELATIONAL_EXPR_PRECEDENCE = 3;
/** add/subtract precedence */
protected static final int ADD_PRECEDENCE = 4;
/** multiply/divide/mod precedence */
protected static final int MULTIPLY_PRECEDENCE = 5;
/** negate precedence */
protected static final int NEGATE_PRECEDENCE = 6;
/** union precedence */
protected static final int UNION_PRECEDENCE = 7;
/**
* Create a new CoreOperation.
* @param args Expression[]
*/
public CoreOperation(Expression[] args) {
super(args);
}
public Object compute(EvalContext context) {
return computeValue(context);
}
public abstract Object computeValue(EvalContext context);
/**
* Returns the XPath symbol for this operation, e.g. "+", "div", etc.
* @return String symbol
*/
public abstract String getSymbol();
/**
* Returns true if the operation is not sensitive to the order of arguments,
* e.g. "=", "and" etc, and false if it is, e.g. "<=", "div".
* @return boolean
*/
protected abstract boolean isSymmetric();
/**
* Computes the precedence of the operation.
* @return int precedence
*/
protected abstract int getPrecedence();
public String toString() {
if (args.length == 1) {
return getSymbol() + parenthesize(args[0], false);
}
StringBuffer buffer = new StringBuffer();
for (int i = 0; i < args.length; i++) {
if (i > 0) {
buffer.append(' ');
buffer.append(getSymbol());
buffer.append(' ');
}
buffer.append(parenthesize(args[i], i == 0));
}
return buffer.toString();
}
/**
* Wrap an expression in parens if necessary.
* @param expression other Expression
* @param left whether <code>expression</code> is left of this one.
* @return String
*/
private String parenthesize(Expression expression, boolean left) {
String s = expression.toString();
if (!(expression instanceof CoreOperation)) {
return s;
}
int compared = getPrecedence() - ((CoreOperation) expression).getPrecedence();
if (compared < 0) {
return s;
}
if (compared == 0 && (isSymmetric() || left)) {
return s;
}
return '(' + s + ')';
}
}
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