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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    *      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  
18  package org.apache.commons.math4.legacy.analysis.function;
19  
20  import org.apache.commons.math4.legacy.analysis.differentiation.DerivativeStructure;
21  import org.apache.commons.math4.legacy.analysis.differentiation.UnivariateDifferentiableFunction;
22  
23  /**
24   * Identity function.
25   *
26   * @since 3.0
27   */
28  public class Identity implements UnivariateDifferentiableFunction {
29      /** {@inheritDoc} */
30      @Override
31      public double value(double x) {
32          return x;
33      }
34  
35      /** {@inheritDoc}
36       * @since 3.1
37       */
38      @Override
39      public DerivativeStructure value(final DerivativeStructure t) {
40          return t;
41      }
42  }