/*
 * 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.math.complex;

import org.apache.commons.math.MathRuntimeException;

/**
 * Static implementations of common
 * {@link org.apache.commons.math.complex.Complex} utilities functions.
 *
 * @version $Revision$ $Date$
 */
public class ComplexUtils {

	/**
	 * Default constructor.
	 */
	private ComplexUtils() {
		super();
	}

	/**
	 * Creates a complex number from the given polar representation.
	 * <p>
	 * The value returned is <code>r&middot;e<sup>i&middot;theta</sup></code>,
	 * computed as <code>r&middot;cos(theta) + r&middot;sin(theta)i</code>
	 * </p>
	 * <p>
	 * If either <code>r</code> or <code>theta</code> is NaN, or
	 * <code>theta</code> is infinite, {@link Complex#NaN} is returned.
	 * </p>
	 * <p>
	 * If <code>r</code> is infinite and <code>theta</code> is finite, infinite
	 * or NaN values may be returned in parts of the result, following the rules
	 * for double arithmetic.
	 * 
	 * <pre>
	 * Examples: 
	 * <code>
	 * polar2Complex(INFINITY, &pi;/4) = INFINITY + INFINITY i
	 * polar2Complex(INFINITY, 0) = INFINITY + NaN i
	 * polar2Complex(INFINITY, -&pi;/4) = INFINITY - INFINITY i
	 * polar2Complex(INFINITY, 5&pi;/4) = -INFINITY - INFINITY i </code>
	 * </pre>
	 * </p>
	 * 
	 * @param r
	 *            the modulus of the complex number to create
	 * @param theta
	 *            the argument of the complex number to create
	 * @return <code>r&middot;e<sup>i&middot;theta</sup></code>
	 * @throws IllegalArgumentException
	 *             if r is negative
	 * @since 1.1
	 */
	public static Complex polar2Complex(double r, double theta) {
		if (r < 0) {
			throw MathRuntimeException.createIllegalArgumentException("negative complex module {0}", r);
		}
		return new Complex(r * Math.cos(theta), r * Math.sin(theta));
	}

}
