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 }