001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.jxpath.ri.compiler;
018    
019    import org.apache.commons.jxpath.ri.EvalContext;
020    import org.apache.commons.jxpath.ri.InfoSetUtil;
021    
022    /**
023     * Implementation of {@link Expression} for the operation unary "-".
024     *
025     * @author Dmitri Plotnikov
026     * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
027     */
028    public class CoreOperationNegate extends CoreOperation {
029    
030        /**
031         * Create a new CoreOperationNegate.
032         * @param arg the Expression to negate
033         */
034        public CoreOperationNegate(Expression arg) {
035            super(new Expression[] { arg });
036        }
037    
038        public Object computeValue(EvalContext context) {
039            double a = InfoSetUtil.doubleValue(args[0].computeValue(context));
040            return new Double(-a);
041        }
042    
043        protected int getPrecedence() {
044            return NEGATE_PRECEDENCE;
045        }
046    
047        protected boolean isSymmetric() {
048            return false;
049        }
050    
051        public String getSymbol() {
052            return "-";
053        }
054    }