View Javadoc
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  import org.hipparchus.CalculusFieldElement;
25  
26  /**
27   * An interface representing a univariate real function.
28   * <p>
29   * When a <em>user-defined</em> function encounters an error during
30   * evaluation, the {@link #value(CalculusFieldElement) value} method should throw a
31   * <em>user-defined</em> unchecked exception.</p>
32   * <p>
33   * The following code excerpt shows the recommended way to do that using
34   * a root solver as an example, but the same construct is applicable to
35   * ODE integrators or optimizers.
36   *
37   * <pre>
38   * private static class LocalException extends RuntimeException {
39   *     // The x value that caused the problem.
40   *     private final SomeFieldType x;
41   *
42   *     public LocalException(SomeFieldType x) {
43   *         this.x = x;
44   *     }
45   *
46   *     public double getX() {
47   *         return x;
48   *     }
49   * }
50   *
51   * private static class MyFunction implements FieldUnivariateFunction&lt;SomeFieldType&gt; {
52   *     public SomeFieldType value(SomeFieldType x) {
53   *         SomeFieldType y = hugeFormula(x);
54   *         if (somethingBadHappens) {
55   *           throw new LocalException(x);
56   *         }
57   *         return y;
58   *     }
59   * }
60   *
61   * public void compute() {
62   *     try {
63   *         solver.solve(maxEval, new MyFunction(a, b, c), min, max);
64   *     } catch (LocalException le) {
65   *         // Retrieve the x value.
66   *     }
67   * }
68   * </pre>
69   *<p>
70   * As shown, the exception is local to the user's code and it is guaranteed
71   * that Hipparchus will not catch it.</p>
72   *
73   * @param <T> the type of the field elements
74   * @see UnivariateFunction
75   * @see FieldUnivariateFunction
76   */
77  public interface CalculusFieldUnivariateFunction<T extends CalculusFieldElement<T>> {
78      /**
79       * Compute the value of the function.
80       *
81       * @param x Point at which the function value should be computed.
82       * @return the value of the function.
83       * @throws IllegalArgumentException when the activated method itself can
84       * ascertain that a precondition, specified in the API expressed at the
85       * level of the activated method, has been violated.
86       * When Hipparchus throws an {@code IllegalArgumentException}, it is
87       * usually the consequence of checking the actual parameters passed to
88       * the method.
89       */
90      T value(T x);
91  }