001/*
002*   ScalarFunctionND  -- Defines an n-Dimensional sclar function y=fn(x[1..n]).
003*
004*   Copyright (C) 2010-2025, by Joseph A. Huwaldt. All rights reserved.
005*   
006*   This library is free software; you can redistribute it and/or
007*   modify it under the terms of the GNU Lesser General Public
008*   License as published by the Free Software Foundation; either
009*   version 2 of the License, or (at your option) any later version.
010*   
011*   This library is distributed in the hope that it will be useful,
012*   but WITHOUT ANY WARRANTY; without even the implied warranty of
013*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014*   Lesser General Public License for more details.
015*
016*   You should have received a copy of the GNU Lesser General Public License
017*   along with this program; if not, write to the Free Software
018*   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
019*   Or visit:  http://www.gnu.org/licenses/lgpl.html
020*/
021package jahuwaldt.tools.math;
022
023/**
024 * A class that defines an n-Dimensional scalar function y = fn(x[1..n]) (named
025 * "function") that can be called by math tools such as a function minimizer. Also defines
026 * the derivatives of the function in each dimension: (dy/dx)[1..n] = d fn(x[1..n])/dx
027 * (oddly enough, named "derivatives").
028 *
029 * <p> Modified by: Joseph A. Huwaldt  </p>
030 *
031 * @author Joseph A. Huwaldt Date: July 9, 2010
032 * @version February 23, 2025
033 */
034public interface ScalarFunctionND {
035
036    /**
037     * User supplied method that calculates the function y = fn(x[1..n]).
038     *
039     * @param x Independent parameters to the function, passed in as input.
040     * @return The scalar function value for the provided list of inputs.
041     * @throws RootException if there is a problem computing the function.
042     */
043    public double function(double x[]) throws RootException;
044
045    /**
046     * User supplied method that calculates the derivatives of the function: (dy/dx)[1..n]
047     * = d( fn(x[1..n]))/dx.
048     *
049     * @param x    Independent parameters to the function, passed in as input.
050     * @param dydx Existing array that is filled in with the derivatives of the function
051     *             with respect to each variable x[i].
052     * @return <code>true</code> if the derivatives were computed by this method,
053     * <code>false</code> if they were not.
054     * @throws RootException if there is a problem computing the derivative.
055     */
056    public boolean derivatives(double[] x, double[] dydx);
057
058}