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
018 package org.apache.commons.math3.analysis.function;
019
020 import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction;
021 import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
022 import org.apache.commons.math3.analysis.differentiation.UnivariateDifferentiableFunction;
023
024 /**
025 * Identity function.
026 *
027 * @since 3.0
028 * @version $Id: Identity.java 1424087 2012-12-19 20:32:50Z luc $
029 */
030 public class Identity implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction {
031 /** {@inheritDoc} */
032 public double value(double x) {
033 return x;
034 }
035
036 /** {@inheritDoc}
037 * @deprecated as of 3.1, replaced by {@link #value(DerivativeStructure)}
038 */
039 @Deprecated
040 public DifferentiableUnivariateFunction derivative() {
041 return new Constant(1);
042 }
043
044 /** {@inheritDoc}
045 * @since 3.1
046 */
047 public DerivativeStructure value(final DerivativeStructure t) {
048 return t;
049 }
050
051 }