Difference.java

/*
 * Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2006.
 *
 * Licensed under the Aduna BSD-style license.
 */
package org.openrdf.query.algebra;

import java.util.Set;

/**
 * The MINUS set operator, which returns the result of the left tuple
 * expression, except for the results that are also returned by the right tuple
 * expression.
 */
public class Difference extends BinaryTupleOperator {

	/*--------------*
	 * Constructors *
	 *--------------*/

	public Difference() {
	}

	/**
	 * Creates a new minus operator that operates on the two specified arguments.
	 * 
	 * @param leftArg
	 *        The left argument of the minus operator.
	 * @param rightArg
	 *        The right argument of the minus operator.
	 */
	public Difference(TupleExpr leftArg, TupleExpr rightArg) {
		super(leftArg, rightArg);
	}

	/*---------*
	 * Methods *
	 *---------*/

	public Set<String> getBindingNames() {
		return getLeftArg().getBindingNames();
	}

	public <X extends Exception> void visit(QueryModelVisitor<X> visitor)
		throws X
	{
		visitor.meet(this);
	}

	@Override
	public Difference clone() {
		return (Difference)super.clone();
	}
}