/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program 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; version 2 of the License.
This program 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.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Sep 24, 2008
*/
package com.bigdata.bop.solutions;
import java.io.Serializable;
import com.bigdata.bop.IBind;
import com.bigdata.bop.IConstant;
import com.bigdata.bop.IValueExpression;
import com.bigdata.bop.IVariable;
/**
* A value expression and a direction flag for the ordering of the computed
* values.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public interface ISortOrder<E> extends Serializable {
/**
* An {@link IValueExpression} to be evaluated for each input solution. The
* {@link IValueExpression} should be either a bare {@link IVariable}, a
* {@link IConstant} or an {@link IBind} associating the computed value of
* an {@link IValueExpression} with an {@link IVariable} bound on the
* solution as a side-effect.
*/
IValueExpression<E> getExpr();
/**
* <code>true</code> iff the values will be placed into an ascending sort
* and <code>false</code> if the values will be placed into a descending
* sort.
*/
boolean isAscending();
}