1 /*
2 * Copyright (C) 2023 Alberto Irurueta Carro (alberto@irurueta.com)
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package com.irurueta.numerical.integration;
17
18 import com.irurueta.numerical.EvaluationException;
19 import com.irurueta.numerical.SingleDimensionFunctionEvaluatorListener;
20
21 /**
22 * This is an exact replacement for MidPointQuadrature i.e., returns the nth stage of refinement of
23 * the integral of a function from "a" to "b", except that the function is evaluated at evenly spaced
24 * points in 1=x rather than in x. This allows the upper limit "b" to be as large and positive as the
25 * computer allows, or the lower limit "a" to be as large and negative, but not both. "a" and "b" must
26 * have the same sign.
27 */
28 public class InfinityMidPointQuadrature extends MidPointQuadrature {
29 /**
30 * Constructor.
31 *
32 * @param a Lower limit of integration.
33 * @param b Upper limit of integration.
34 * @param listener listener to evaluate a single dimension function at required points.
35 */
36 public InfinityMidPointQuadrature(
37 final double a, final double b, final SingleDimensionFunctionEvaluatorListener listener) {
38 super(1.0 / b, 1.0 / a, listener);
39 }
40
41 /**
42 * Gets type of quadrature.
43 *
44 * @return type of quadrature.
45 */
46 @Override
47 public QuadratureType getType() {
48 return QuadratureType.INFINITY_MID_POINT;
49 }
50
51 /**
52 * Evaluates function at 1/x.
53 *
54 * @param x point where function is evaluated.
55 * @return result of evaluation.
56 * @throws EvaluationException if evaluation fails.
57 */
58 @Override
59 protected double func(final double x) throws EvaluationException {
60 return listener.evaluate(1.0 / x) / (x * x);
61 }
62 }