| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.numbers.fraction; |
| |
| import java.util.Locale; |
| import org.junit.jupiter.api.Assertions; |
| import org.junit.jupiter.api.Test; |
| |
| /** |
| * Tests for {@link ContinuedFraction}. |
| */ |
| public class ContinuedFractionTest { |
| |
| @Test |
| public void testGoldenRatio() throws Exception { |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return 1; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return 1; |
| } |
| }; |
| |
| final double eps = 1e-8; |
| double gr = cf.evaluate(0, eps); |
| Assertions.assertEquals(1.61803399, gr, eps); |
| } |
| |
| @Test |
| public void test415Over93() throws Exception { |
| // https://en.wikipedia.org/wiki/Continued_fraction |
| // 415 1 |
| // --- = 4 + --------- |
| // 93 2 + 1 |
| // ----- |
| // 6 + 1 |
| // - |
| // 7 |
| // = [4; 2, 6, 7] |
| |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return n <= 3 ? 1 : 0; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| switch (n) { |
| case 0: return 4; |
| case 1: return 2; |
| case 2: return 6; |
| case 3: return 7; |
| default: return 1; |
| } |
| } |
| }; |
| |
| final double eps = 1e-8; |
| double gr = cf.evaluate(0, eps, 5); |
| Assertions.assertEquals(415.0 / 93.0, gr, eps); |
| } |
| |
| @Test |
| public void testMaxIterationsThrows() throws Exception { |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return 1; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return 1; |
| } |
| }; |
| |
| final double eps = 1e-8; |
| final int maxIterations = 3; |
| final Throwable t = Assertions.assertThrows(FractionException.class, |
| () -> cf.evaluate(0, eps, maxIterations)); |
| assertExceptionMessageContains(t, "max"); |
| } |
| |
| @Test |
| public void testNaNThrows() throws Exception { |
| // Create a NaN during the iteration |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return 1; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return n == 0 ? 1 : Double.NaN; |
| } |
| }; |
| |
| final double eps = 1e-8; |
| final Throwable t = Assertions.assertThrows(FractionException.class, |
| () -> cf.evaluate(0, eps, 5)); |
| assertExceptionMessageContains(t, "nan"); |
| } |
| |
| @Test |
| public void testInfThrows() throws Exception { |
| // Create an infinity during the iteration: |
| // a / cPrev => a_1 / b_0 => Double.MAX_VALUE / 0.5 |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return n == 0 ? 1 : Double.MAX_VALUE; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return 0.5; |
| } |
| }; |
| |
| final double eps = 1e-8; |
| final Throwable t = Assertions.assertThrows(FractionException.class, |
| () -> cf.evaluate(0, eps, 5)); |
| assertExceptionMessageContains(t, "infinity"); |
| } |
| |
| private static void assertExceptionMessageContains(Throwable t, String text) { |
| Assertions.assertTrue(t.getMessage().toLowerCase(Locale.ROOT).contains(text), |
| () -> "Missing '" + text + "' from exception message: " + t.getMessage()); |
| } |
| |
| // NUMBERS-46 |
| @Test |
| public void testOneIteration() { |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return 1; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return 1; |
| } |
| }; |
| |
| final double eps = 10; |
| double gr = cf.evaluate(0, eps, 1); |
| Assertions.assertEquals(1.61, gr, eps); |
| } |
| |
| // NUMBERS-46 |
| @Test |
| public void testTwoIterations() { |
| ContinuedFraction cf = new ContinuedFraction() { |
| @Override |
| public double getA(int n, double x) { |
| return 1; |
| } |
| |
| @Override |
| public double getB(int n, double x) { |
| return 1; |
| } |
| }; |
| |
| final double eps = 0.5; |
| double gr = cf.evaluate(0, eps, 2); |
| Assertions.assertEquals(1.5, gr, 0d); |
| } |
| } |