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 * https://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
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22 package org.hipparchus.analysis;
23
24 /**
25 * An interface representing a univariate real function.
26 * <p>
27 * When a <em>user-defined</em> function encounters an error during
28 * evaluation, the {@link #value(double) value} method should throw a
29 * <em>user-defined</em> unchecked exception.</p>
30 * <p>
31 * The following code excerpt shows the recommended way to do that using
32 * a root solver as an example, but the same construct is applicable to
33 * ODE integrators or optimizers.</p>
34 *
35 * <pre>
36 * private static class LocalException extends RuntimeException {
37 * // The x value that caused the problem.
38 * private final double x;
39 *
40 * public LocalException(double x) {
41 * this.x = x;
42 * }
43 *
44 * public double getX() {
45 * return x;
46 * }
47 * }
48 *
49 * private static class MyFunction implements UnivariateFunction {
50 * public double value(double x) {
51 * double 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 *
68 * As shown, the exception is local to the user's code and it is guaranteed
69 * that Hipparchus will not catch it.
70 *
71 */
72 public interface UnivariateFunction {
73 /**
74 * Compute the value of the function.
75 *
76 * @param x Point at which the function value should be computed.
77 * @return the value of the function.
78 * @throws IllegalArgumentException when the activated method itself can
79 * ascertain that a precondition, specified in the API expressed at the
80 * level of the activated method, has been violated.
81 * When Hipparchus throws an {@code IllegalArgumentException}, it is
82 * usually the consequence of checking the actual parameters passed to
83 * the method.
84 */
85 double value(double x);
86 }