001/* An interface for tokens that can be partially ordered.
002
003 Copyright (c) 2010-2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026 */
027package ptolemy.data;
028
029import ptolemy.data.expr.ASTPtRelationalNode;
030import ptolemy.kernel.util.IllegalActionException;
031
032/** An interface for tokens that can be partially ordered.
033
034 <p>The default implementation of visitRelationalNode
035 {@link ptolemy.data.expr.ParseTreeEvaluator#visitRelationalNode(ASTPtRelationalNode)}
036 uses this interface, so any tokens that implement this interface can be used
037 with the inequality operators (&lt;, &le;, &gt;, and &ge;) in the Ptolemy expression
038 language.
039
040 @author Ben Lickly
041 @since Ptolemy II 10.0
042 @Pt.ProposedRating Red (blickly)
043 @Pt.AcceptedRating Red (blickly)
044 */
045public interface PartiallyOrderedToken {
046    // FIXME: Should this be a class below ptolemy.data.Token but
047    // above ptolemy.data.ScalarToken and
048    // ptolemy.data.ontologies.ConceptToken} rather than an interface?
049
050    /** Check whether the value of this token is strictly less than that of the
051     *  argument token.
052     *
053     *  Only a partial order is assumed, so !(a &lt; b) need not imply (a &ge; b).
054     *
055     *  @param rightArgument The token on greater than side of the inequality.
056     *  @return BooleanToken.TRUE, if this token is less than the
057     *    argument token. BooleanToken.FALSE, otherwise.
058     *  @exception IllegalActionException If the tokens are incomparable.
059     */
060    public abstract BooleanToken isLessThan(PartiallyOrderedToken rightArgument)
061            throws IllegalActionException;
062}