1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math4.legacy.analysis;
18
19 import org.apache.commons.math4.legacy.core.RealFieldElement;
20
21 /**
22 * An interface representing a univariate real function.
23 * <p>
24 * When a <em>user-defined</em> function encounters an error during
25 * evaluation, the {@link #value(RealFieldElement) value} method should throw a
26 * <em>user-defined</em> unchecked exception.</p>
27 * <p>
28 * The following code excerpt shows the recommended way to do that using
29 * a root solver as an example, but the same construct is applicable to
30 * ODE integrators or optimizers.
31 *
32 * <pre>
33 * private static class LocalException extends RuntimeException {
34 * // The x value that caused the problem.
35 * private final SomeFieldType x;
36 *
37 * LocalException(SomeFieldType x) {
38 * this.x = x;
39 * }
40 *
41 * SomeFieldType getX() {
42 * return x;
43 * }
44 * }
45 *
46 * private static class MyFunction implements FieldUnivariateFunction<SomeFieldType> {
47 *
48 * // ... function set-up
49 *
50 * public SomeFieldType value(SomeFieldType x) {
51 * SomeFieldType y = hugeFormula(x);
52 * if (somethingBadHappens) {
53 * throw new LocalException(x);
54 * }
55 * return y;
56 * }
57 * }
58 *
59 * public void compute() {
60 * try {
61 * solver.solve(maxEval, new MyFunction(a, b, c), min, max);
62 * } catch (LocalException le) {
63 * // Retrieve the x value.
64 * }
65 * }
66 * </pre>
67 *<p>
68 * As shown, the exception is local to the user's code and it is guaranteed
69 * that Apache Commons Math will not catch it.</p>
70 *
71 * @param <T> the type of the field elements
72 * @since 3.6
73 * @see UnivariateFunction
74 */
75 public interface RealFieldUnivariateFunction<T extends RealFieldElement<T>> {
76 /**
77 * Compute the value of the function.
78 *
79 * @param x Point at which the function value should be computed.
80 * @return the value of the function.
81 * @throws IllegalArgumentException when the activated method itself can
82 * ascertain that a precondition, specified in the API expressed at the
83 * level of the activated method, has been violated.
84 * When Commons Math throws an {@code IllegalArgumentException}, it is
85 * usually the consequence of checking the actual parameters passed to
86 * the method.
87 */
88 T value(T x);
89 }