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Java > Open Source Codes > com > icl > saxon > functions > ElementAvailable


1 package com.icl.saxon.functions;
2 import com.icl.saxon.*;
3 import com.icl.saxon.om.Namespace;
4 import com.icl.saxon.expr.*;
5 import com.icl.saxon.style.*;
6
7 import java.util.*;
8
9
10 public class ElementAvailable extends Function {
11
12     /**
13     * Function name (for diagnostics)
14     */
15
16     public String JavaDoc getName() {
17         return "element-available";
18     };
19
20     /**
21     * Determine the data type of the expression
22     * @return Value.BOOLEAN
23     */
24
25     public int getDataType() {
26         return Value.BOOLEAN;
27     }
28
29     /**
30     * Simplify and validate.
31     * This is a pure function so it can be simplified in advance if the arguments are known
32     */
33
34     public Expression simplify() throws XPathException {
35         checkArgumentCount(1, 1);
36         argument[0] = argument[0].simplify();
37         if (argument[0] instanceof Value) {
38             return evaluate(null);
39         }
40         return this;
41     }
42
43     /**
44     * Evaluate the function in a boolean context
45     */
46
47     public boolean evaluateAsBoolean(Context c) throws XPathException {
48         String JavaDoc qname = argument[0].evaluateAsString(c);
49         return getStaticContext().isElementAvailable(qname);
50     }
51
52     /**
53     * Evaluate in a general context
54     */
55
56     public Value evaluate(Context c) throws XPathException {
57         return new BooleanValue(evaluateAsBoolean(c));
58     }
59
60     /**
61     * Determine the dependencies
62     */
63
64     public int getDependencies() {
65         return argument[0].getDependencies();
66     }
67
68     /**
69     * Reduce the dependencies
70     */
71
72     public Expression reduce(int dep, Context c) throws XPathException {
73         ElementAvailable f = new ElementAvailable();
74         f.addArgument(argument[0].reduce(dep, c));
75         f.setStaticContext(getStaticContext());
76         return f.simplify();
77     }
78
79     /**
80     * Get the factory class for user extension elements
81     */
82
83     //private ExtensionElementFactory getFactory(String uri) throws XPathException {
84 // int lastSlash = uri.lastIndexOf('/');
85 // if (lastSlash<0 || lastSlash==uri.length()-1) {
86 // return null;
87 // }
88 // String factoryClass = uri.substring(lastSlash+1);
89 // ExtensionElementFactory factory;
90 //
91 // try {
92 // return (ExtensionElementFactory)Loader.getInstance(factoryClass);
93 // } catch (Exception err) {
94 // return null;
95 // }
96 ///}
97
98 }
99
100
101
102 //
103 // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
104 // you may not use this file except in compliance with the License. You may obtain a copy of the
105 // License at http://www.mozilla.org/MPL/
106 //
107 // Software distributed under the License is distributed on an "AS IS" basis,
108 // WITHOUT WARRANTY OF ANY KIND, either express or implied.
109 // See the License for the specific language governing rights and limitations under the License.
110 //
111 // The Original Code is: all this file.
112 //
113 // The Initial Developer of the Original Code is
114 // Michael Kay of International Computers Limited (mhkay@iclway.co.uk).
115 //
116 // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
117 //
118 // Contributor(s): none.
119 //
120
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