1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math.analysis;
18  
19  import org.apache.commons.math.FunctionEvaluationException;
20  
21  /**
22   * Auxillary class for testing purposes.
23   *
24   * @version $Revision: 786927 $ $Date: 2009-06-20 19:37:47 -0400 (Sat, 20 Jun 2009) $
25   */
26  public class Expm1Function implements DifferentiableUnivariateRealFunction {
27  
28      public double value(double x) throws FunctionEvaluationException {
29          // Math.expm1() is available in jdk 1.5 but not in jdk 1.4.2.
30          return Math.exp(x) - 1.0;
31      }
32  
33      public UnivariateRealFunction derivative() {
34          return new UnivariateRealFunction() {
35              public double value(double x) throws FunctionEvaluationException {
36                  return Math.exp(x);
37              }
38          };
39      }
40  }