- /*
- * Copyright 1999-2004 The Apache Software Foundation
- *
- * Licensed 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: 1.14 $ $Date: 2004/02/29 14:17:39 $
- */
- public abstract class CoreOperation extends Operation {
-
- 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.
- */
- 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".
- */
- protected abstract boolean isSymmetric();
-
- /**
- * Computes the precedence of the operation.
- */
- protected abstract int getPrecedence();
-
- public String toString() {
- if (args.length == 1) {
- return getSymbol() + parenthesize(args[0], false);
- }
- else {
- 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();
- }
- }
-
- private String parenthesize(Expression expression, boolean left) {
- if (!(expression instanceof CoreOperation)) {
- return expression.toString();
- }
- CoreOperation op = (CoreOperation) expression;
- int myPrecedence = getPrecedence();
- int thePrecedence = op.getPrecedence();
-
- boolean needParens = true;
- if (myPrecedence < thePrecedence) {
- needParens = false;
- }
- else if (myPrecedence == thePrecedence) {
- if (isSymmetric()) {
- needParens = false;
- }
- else {
- needParens = !left;
- }
- }
-
- if (needParens) {
- return "(" + expression.toString() + ")";
- }
- else {
- return expression.toString();
- }
- }
- }