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&middot;e<sup>i&middot;theta</sup></code>,
043         * computed as <code>r&middot;cos(theta) + r&middot;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, &pi;/4) = INFINITY + INFINITY i
054         * polar2Complex(INFINITY, 0) = INFINITY + NaN i
055         * polar2Complex(INFINITY, -&pi;/4) = INFINITY - INFINITY i
056         * polar2Complex(INFINITY, 5&pi;/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&middot;e<sup>i&middot;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    }