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
18package org.apache.commons.math.complex;
19
20import org.apache.commons.math.MathRuntimeException;
21import org.apache.commons.math.exception.util.LocalizedFormats;
22import org.apache.commons.math.util.FastMath;
23
24/**
25 * Static implementations of common
26 * {@link org.apache.commons.math.complex.Complex} utilities functions.
27 *
28 * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 août 2010) $
29 */
30public class ComplexUtils {
31
32    /**
33     * Default constructor.
34     */
35    private ComplexUtils() {
36        super();
37    }
38
39    /**
40     * Creates a complex number from the given polar representation.
41     * <p>
42     * The value returned is <code>r&middot;e<sup>i&middot;theta</sup></code>,
43     * computed as <code>r&middot;cos(theta) + r&middot;sin(theta)i</code></p>
44     * <p>
45     * If either <code>r</code> or <code>theta</code> is NaN, or
46     * <code>theta</code> is infinite, {@link Complex#NaN} is returned.</p>
47     * <p>
48     * If <code>r</code> is infinite and <code>theta</code> is finite,
49     * infinite or NaN values may be returned in parts of the result, following
50     * the rules for double arithmetic.<pre>
51     * Examples:
52     * <code>
53     * polar2Complex(INFINITY, &pi;/4) = INFINITY + INFINITY i
54     * polar2Complex(INFINITY, 0) = INFINITY + NaN i
55     * polar2Complex(INFINITY, -&pi;/4) = INFINITY - INFINITY i
56     * polar2Complex(INFINITY, 5&pi;/4) = -INFINITY - INFINITY i </code></pre></p>
57     *
58     * @param r the modulus of the complex number to create
59     * @param theta  the argument of the complex number to create
60     * @return <code>r&middot;e<sup>i&middot;theta</sup></code>
61     * @throws IllegalArgumentException  if r is negative
62     * @since 1.1
63     */
64    public static Complex polar2Complex(double r, double theta) {
65        if (r < 0) {
66            throw MathRuntimeException.createIllegalArgumentException(
67                  LocalizedFormats.NEGATIVE_COMPLEX_MODULE, r);
68        }
69        return new Complex(r * FastMath.cos(theta), r * FastMath.sin(theta));
70    }
71
72}
73