//******************************************************************************
//
// File:    ObjectOp.java
// Package: edu.rit.pj.reduction
// Unit:    Class edu.rit.pj.reduction.ObjectOp
//
// This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ 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 GNU General Public License for more details.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.pj.reduction;

/**
 * Class ObjectOp is the abstract base class for a binary operation on object
 * values, used to do reduction in a parallel program.
 * 

 * When classes in the Parallel Java Library call the op(x,y) method
 * during a reduction operation, the x argument is the value of the
 * reduction variable, and the y argument is the value to be combined
 * with the reduction variable. The value returned by the op(x,y)
 * method is stored back into the reduction variable.
 * 

 * The op(x,y) method in any subclass of class ObjectOp must obey the
 * following requirements, which are assumed by classes in the Parallel Java
 * Library:
 * 

 * 

 * If as a result of the binary operation the state of the reduction variable
 * will not change, the op(x,y) method must return x.
 * 

 * If as a result of the binary operation the state of the reduction variable
 * will change, the op(x,y) method must return a newly created object
 * containing the desired state.
 * 

 * The op(x,y) method must neither change the state of x nor
 * change the state of y; that is, the op(x,y) method must
 * have no side effects.
 * 
 *
 * @param    Object data type.
 *
 * @author  Alan Kaminsky
 * @version 30-Mar-2008
 */
public abstract class ObjectOp
	extends Op
	{

// Hidden constructors.

	/**
	 * Construct a new object binary operation.
	 */
	protected ObjectOp()
		{
		super();
		}

// Exported operations.

	/**
	 * Perform this binary operation.
	 *
	 * @param  x  First argument.
	 * @param  y  Second argument.
	 *
	 * @return  (x op y), where op stands for
	 *          this binary operation.
	 */
	public abstract T op
		(T x,
		 T y);

	}