1 // ******************************************************************************
2 //
3 // Title: Force Field X.
4 // Description: Force Field X - Software for Molecular Biophysics.
5 // Copyright: Copyright (c) Michael J. Schnieders 2001-2025.
6 //
7 // This file is part of Force Field X.
8 //
9 // Force Field X is free software; you can redistribute it and/or modify it
10 // under the terms of the GNU General Public License version 3 as published by
11 // the Free Software Foundation.
12 //
13 // Force Field X is distributed in the hope that it will be useful, but WITHOUT
14 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
15 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
16 // details.
17 //
18 // You should have received a copy of the GNU General Public License along with
19 // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
20 // Place, Suite 330, Boston, MA 02111-1307 USA
21 //
22 // Linking this library statically or dynamically with other modules is making a
23 // combined work based on this library. Thus, the terms and conditions of the
24 // GNU General Public License cover the whole combination.
25 //
26 // As a special exception, the copyright holders of this library give you
27 // permission to link this library with independent modules to produce an
28 // executable, regardless of the license terms of these independent modules, and
29 // to copy and distribute the resulting executable under terms of your choice,
30 // provided that you also meet, for each linked independent module, the terms
31 // and conditions of the license of that module. An independent module is a
32 // module which is not derived from or based on this library. If you modify this
33 // library, you may extend this exception to your version of the library, but
34 // you are not obligated to do so. If you do not wish to do so, delete this
35 // exception statement from your version.
36 //
37 // ******************************************************************************
38 package ffx.numerics.func1d;
39
40 /**
41 * A UnivariateDiffFunction describes a function of a single value (often lambda). Generally, it
42 * should be at least twice differentiable.
43 *
44 * @author Jacob M. Litman
45 * @author Michael J. Schnieders
46 */
47 public interface UnivariateDiffFunction {
48
49 /**
50 * First derivative at a point.
51 *
52 * @param x a double.
53 * @return f'(x)
54 * @throws java.lang.IllegalArgumentException If f'(x) is undefined at x.
55 */
56 double firstDerivative(double x) throws IllegalArgumentException;
57
58 /**
59 * N'th order derivative at a point. Should be relatively optional for any order above 2.
60 *
61 * @param x a double.
62 * @param order Derivative order (>= 1)
63 * @return d^nf(x)/dx^n
64 * @throws java.lang.IllegalArgumentException If derivative undefined at x.
65 */
66 double nthDerivative(double x, int order) throws IllegalArgumentException;
67
68 /**
69 * Second derivative at a point.
70 *
71 * @param x a double.
72 * @return f''(x)
73 * @throws java.lang.IllegalArgumentException If f''(x) is undefined at x.
74 */
75 double secondDerivative(double x) throws IllegalArgumentException;
76
77 /**
78 * Value at a point
79 *
80 * @param x a double.
81 * @return f(x)
82 * @throws java.lang.IllegalArgumentException If f(x) is undefined at x.
83 */
84 double valueAt(double x) throws IllegalArgumentException;
85 }