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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    *      https://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  
18  /*
19   * This is not the original file distributed by the Apache Software Foundation
20   * It has been modified by the Hipparchus project
21   */
22  
23  package org.hipparchus.analysis.function;
24  
25  import org.hipparchus.analysis.differentiation.Derivative;
26  import org.hipparchus.analysis.differentiation.UnivariateDifferentiableFunction;
27  import org.hipparchus.util.FastMath;
28  
29  /**
30   * Natural logarithm function.
31   *
32   */
33  public class Log implements UnivariateDifferentiableFunction {
34  
35      /** Empty constructor.
36       * <p>
37       * This constructor is not strictly necessary, but it prevents spurious
38       * javadoc warnings with JDK 18 and later.
39       * </p>
40       * @since 3.0
41       */
42      public Log() { // NOPMD - unnecessary constructor added intentionally to make javadoc happy
43          // nothing to do
44      }
45  
46      /** {@inheritDoc} */
47      @Override
48      public double value(double x) {
49          return FastMath.log(x);
50      }
51  
52      /** {@inheritDoc} */
53      @Override
54      public <T extends Derivative<T>> T value(T x) {
55          return x.log();
56      }
57  
58  }