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Java > Open Source Codes > com > hp > hpl > jena > reasoner > rulesys > builtins > Equal


1 /******************************************************************
2  * File: Equal.java
3  * Created by: Dave Reynolds
4  * Created on: 24-Aug-2003
5  *
6  * (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP
7  * [See end of file]
8  * $Id: Equal.java,v 1.6 2005/02/21 12:17:22 andy_seaborne Exp $
9  *****************************************************************/
10 package com.hp.hpl.jena.reasoner.rulesys.builtins;
11
12 import com.hp.hpl.jena.reasoner.rulesys.*;
13 import com.hp.hpl.jena.graph.*;
14
15 // Thanks to Bradley Schatz (Bradley@greystate.com) for code patches
16 // to support XSDDateTime comparisons
17
18 /**
19  * Check that the two args are semantically equal.
20  *
21  * @author <a HREF="mailto:der@hplb.hpl.hp.com">Dave Reynolds</a>
22  * @version $Revision: 1.6 $ on $Date: 2005/02/21 12:17:22 $
23  */
24 public class Equal extends BaseBuiltin {
25
26     /**
27      * Return a name for this builtin, normally this will be the name of the
28      * functor that will be used to invoke it.
29      */
30     public String JavaDoc getName() {
31         return "equal";
32     }
33     
34     /**
35      * Return the expected number of arguments for this functor or 0 if the number is flexible.
36      */
37     public int getArgLength() {
38         return 2;
39     }
40
41     /**
42      * This method is invoked when the builtin is called in a rule body.
43      * @param args the array of argument values for the builtin, this is an array
44      * of Nodes, some of which may be Node_RuleVariables.
45      * @param length the length of the argument list, may be less than the length of the args array
46      * for some rule engines
47      * @param context an execution context giving access to other relevant data
48      * @return return true if the buildin predicate is deemed to have succeeded in
49      * the current environment
50      */
51     public boolean bodyCall(Node[] args, int length, RuleContext context) {
52         checkArgs(length, context);
53         Node n1 = getArg(0, args, context);
54         Node n2 = getArg(1, args, context);
55         if (Util.isNumeric(n1)) {
56             return Util.compareNumbers(n1, n2) == 0;
57         } else if (Util.isInstant(n1) && Util.isInstant(n2)) {
58             return Util.compareInstants(n1, n2) == 0;
59         } else {
60             return n1.sameValueAs(n2);
61         }
62     }
63     
64 }
65
66
67 /*
68     (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP
69     All rights reserved.
70
71     Redistribution and use in source and binary forms, with or without
72     modification, are permitted provided that the following conditions
73     are met:
74
75     1. Redistributions of source code must retain the above copyright
76        notice, this list of conditions and the following disclaimer.
77
78     2. Redistributions in binary form must reproduce the above copyright
79        notice, this list of conditions and the following disclaimer in the
80        documentation and/or other materials provided with the distribution.
81
82     3. The name of the author may not be used to endorse or promote products
83        derived from this software without specific prior written permission.
84
85     THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
86     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
87     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
88     IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
89     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
90     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
91     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
92     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
93     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
94     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
95 */
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