KickJava   Java API By Example, From Geeks To Geeks.

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


1 /******************************************************************
2  * File: ListContains.java
3  * Created by: Dave Reynolds
4  * Created on: 23-Sep-2003
5  *
6  * (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP, all rights reserved.
7  * [See end of file]
8  * $Id: ListContains.java,v 1.6 2005/02/21 12:17:27 andy_seaborne Exp $
9  *****************************************************************/
10 package com.hp.hpl.jena.reasoner.rulesys.builtins;
11
12
13 import com.hp.hpl.jena.reasoner.rulesys.*;
14 import com.hp.hpl.jena.vocabulary.RDF;
15 import com.hp.hpl.jena.graph.*;
16
17 /**
18  * Returns true if the first argument is a list which contains the second argument.
19  * Can't be used as a generator.
20  *
21  * @author <a HREF="mailto:der@hplb.hpl.hp.com">Dave Reynolds</a>
22  * @version $Revision: 1.6 $ on $Date: 2005/02/21 12:17:27 $
23  */
24 public class ListContains 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 "listContains";
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 n0 = getArg(0, args, context);
54         Node n1 = getArg(1, args, context);
55         return listContains(n0, n1, context);
56     }
57     
58     /**
59      * Return true if the first argument is a list which contains
60      * the second argument.
61      */
62     protected static boolean listContains(Node list, Node element, RuleContext context ) {
63          if (list == null || list.equals(RDF.Nodes.nil)) {
64              return false;
65          } else {
66              Node elt = Util.getPropValue(list, RDF.Nodes.first, context);
67              if (elt.sameValueAs(element)) {
68                  return true;
69              } else {
70                  Node next = Util.getPropValue(list, RDF.Nodes.rest, context);
71                  return listContains(next, element, context);
72              }
73          }
74     }
75 }
76
77
78 /*
79     (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP
80     All rights reserved.
81
82     Redistribution and use in source and binary forms, with or without
83     modification, are permitted provided that the following conditions
84     are met:
85
86     1. Redistributions of source code must retain the above copyright
87        notice, this list of conditions and the following disclaimer.
88
89     2. Redistributions in binary form must reproduce the above copyright
90        notice, this list of conditions and the following disclaimer in the
91        documentation and/or other materials provided with the distribution.
92
93     3. The name of the author may not be used to endorse or promote products
94        derived from this software without specific prior written permission.
95
96     THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
97     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
98     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
99     IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
100     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
101     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
102     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
103     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
104     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
105     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
106 */
Popular Tags