    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     * Constant function.
    026     *
    027     * @since 3.0
    028     * @version $Id: Constant.java 1424087 2012-12-19 20:32:50Z luc $
    029     */
    030    public class Constant implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction {
    031        /** Constant. */
    032        private final double c;
    033
    034        /**
    035         * @param c Constant.
    036         */
    037        public Constant(double c) {
    038            this.c = c;
    039        }
    040
    041        /** {@inheritDoc} */
    042        public double value(double x) {
    043            return c;
    044        }
    045
    046        /** {@inheritDoc}
    047         * @deprecated as of 3.1, replaced by {@link #value(DerivativeStructure)}
    048         */
    049        @Deprecated
    050        public DifferentiableUnivariateFunction derivative() {
    051            return new Constant(0);
    052        }
    053
    054        /** {@inheritDoc}
    055         * @since 3.1
    056         */
    057        public DerivativeStructure value(final DerivativeStructure t) {
    058            return new DerivativeStructure(t.getFreeParameters(), t.getOrder(), c);
    059        }
    060
    061    }