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/*************************************************************************
 *                                                                       *
 * Open Dynamics Engine 4J, Copyright (C) 2009-2014 Tilmann Zaeschke     *
 * All rights reserved.  Email: [email protected]   Web: www.ode4j.org        *
 *                                                                       *
 * This library is free software; you can redistribute it and/or         *
 * modify it under the terms of EITHER:                                  *
 *   (1) The GNU Lesser General Public License as published by the Free  *
 *       Software Foundation; either version 2.1 of the License, or (at  *
 *       your option) any later version. The text of the GNU Lesser      *
 *       General Public License is included with this library in the     *
 *       file LICENSE.TXT.                                               *
 *   (2) The BSD-style license that is included with this library in     *
 *       the file ODE4J-LICENSE-BSD.TXT.                                 *
 *                                                                       *
 * This library is distributed in the hope that it will be useful,       *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
 * LICENSE.TXT and ODE4J-LICENSE-BSD.TXT for more details.               *
 *                                                                       *
 *************************************************************************/
package org.ode4j.math;

/**
 * Constant (unmodifiable) interface for DQuaternion.
 * 
 * This returns an unmodifiable view of an (most likely) modifiable object.
 * 
 * A quaternion consists of four numbers, [w, x, y, z].
 * They are used top represent rigid body orientations. 
 *  
 * 
 * WARNING: This is only unmodifiable for the user. The class that returned
 * this object may continue to modify it, these changes will also reflect in
 * the 'unmodifiable view' that the user has.
 * If the user requires a lasting immutable object, then the object needs to 
 * be cloned. 
 *
 * @author Tilmann Zaeschke
 */
public interface DQuaternionC {

	/**
	 * @param i The row to return [0, 1, 2].
	 */
	public double get(int i);

	/**
	 * w of [w, x, y, z].
	 * @return w
	 */
	public double get0();

	/**
	 * x of [w, x, y, z].
	 * @return x
	 */
	public double get1();

	/**
	 * y of [w, x, y, z].
	 * @return y
	 */
	public double get2();

	/**
	 * z of [w, x, y, z].
	 * @return z
	 */
	public double get3();
}