001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.math.complex;
019
020 import org.apache.commons.math.MathRuntimeException;
021 import org.apache.commons.math.exception.util.LocalizedFormats;
022 import org.apache.commons.math.util.FastMath;
023
024 /**
025 * Static implementations of common
026 * {@link org.apache.commons.math.complex.Complex} utilities functions.
027 *
028 * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 ao??t 2010) $
029 */
030 public class ComplexUtils {
031
032 /**
033 * Default constructor.
034 */
035 private ComplexUtils() {
036 super();
037 }
038
039 /**
040 * Creates a complex number from the given polar representation.
041 * <p>
042 * The value returned is <code>r·e<sup>i·theta</sup></code>,
043 * computed as <code>r·cos(theta) + r·sin(theta)i</code></p>
044 * <p>
045 * If either <code>r</code> or <code>theta</code> is NaN, or
046 * <code>theta</code> is infinite, {@link Complex#NaN} is returned.</p>
047 * <p>
048 * If <code>r</code> is infinite and <code>theta</code> is finite,
049 * infinite or NaN values may be returned in parts of the result, following
050 * the rules for double arithmetic.<pre>
051 * Examples:
052 * <code>
053 * polar2Complex(INFINITY, π/4) = INFINITY + INFINITY i
054 * polar2Complex(INFINITY, 0) = INFINITY + NaN i
055 * polar2Complex(INFINITY, -π/4) = INFINITY - INFINITY i
056 * polar2Complex(INFINITY, 5π/4) = -INFINITY - INFINITY i </code></pre></p>
057 *
058 * @param r the modulus of the complex number to create
059 * @param theta the argument of the complex number to create
060 * @return <code>r·e<sup>i·theta</sup></code>
061 * @throws IllegalArgumentException if r is negative
062 * @since 1.1
063 */
064 public static Complex polar2Complex(double r, double theta) {
065 if (r < 0) {
066 throw MathRuntimeException.createIllegalArgumentException(
067 LocalizedFormats.NEGATIVE_COMPLEX_MODULE, r);
068 }
069 return new Complex(r * FastMath.cos(theta), r * FastMath.sin(theta));
070 }
071
072 }