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.math.analysis;
018    
019    import org.apache.commons.math.FunctionEvaluationException;
020    
021    /**
022     * Auxillary class for testing purposes.
023     *
024     * @version $Revision: 786927 $ $Date: 2009-06-20 19:37:47 -0400 (Sat, 20 Jun 2009) $
025     */
026    public class Expm1Function implements DifferentiableUnivariateRealFunction {
027    
028        public double value(double x) throws FunctionEvaluationException {
029            // Math.expm1() is available in jdk 1.5 but not in jdk 1.4.2.
030            return Math.exp(x) - 1.0;
031        }
032    
033        public UnivariateRealFunction derivative() {
034            return new UnivariateRealFunction() {
035                public double value(double x) throws FunctionEvaluationException {
036                    return Math.exp(x);
037                }
038            };
039        }
040    }