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Java > Open Source Codes > org > apache > velocity > runtime > parser > node > ASTSubtractNode


1 package org.apache.velocity.runtime.parser.node;
2
3 /*
4  * Copyright 2000-2001,2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import org.apache.velocity.context.InternalContextAdapter;
20 import org.apache.velocity.runtime.parser.Parser;
21
22 import org.apache.velocity.exception.MethodInvocationException;
23
24 /**
25  * Handles integer subtraction of nodes (in #set() )
26  *
27  * Please look at the Parser.jjt file which is
28  * what controls the generation of this class.
29  *
30  * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
31  * @author <a HREF="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
32  * @version $Id: ASTSubtractNode.java,v 1.7.8.1 2004/03/03 23:22:59 geirm Exp $
33  */
34 public class ASTSubtractNode extends SimpleNode
35 {
36     public ASTSubtractNode(int id)
37     {
38         super(id);
39     }
40
41     public ASTSubtractNode(Parser p, int id)
42     {
43         super(p, id);
44     }
45
46     /** Accept the visitor. **/
47     public Object JavaDoc jjtAccept(ParserVisitor visitor, Object JavaDoc data)
48     {
49         return visitor.visit(this, data);
50     }
51
52     /**
53      * computes the value of the subtraction. Currently
54      * limited to integers
55      * @return Integer(value) or null
56      */
57     public Object JavaDoc value( InternalContextAdapter context)
58         throws MethodInvocationException
59     {
60         /*
61          * get the two args
62          */
63
64         Object JavaDoc left = jjtGetChild(0).value( context );
65         Object JavaDoc right = jjtGetChild(1).value( context );
66
67         /*
68          * if either is null, lets log and bail
69          */
70
71         if (left == null || right == null)
72         {
73             rsvc.error( ( left == null ? "Left" : "Right" ) + " side ("
74                            + jjtGetChild( (left == null? 0 : 1) ).literal()
75                            + ") of subtraction operation has null value."
76                            + " Operation not possible. "
77                            + context.getCurrentTemplateName() + " [line " + getLine()
78                            + ", column " + getColumn() + "]");
79             return null;
80         }
81         
82         /*
83          * if not an Integer, not much we can do either
84          */
85
86         if ( !( left instanceof Integer JavaDoc ) || !( right instanceof Integer JavaDoc ))
87         {
88             rsvc.error( ( !( left instanceof Integer JavaDoc ) ? "Left" : "Right" )
89                            + " side of subtraction operation is not a valid type. "
90                            + "Currently only integers (1,2,3...) and Integer type is supported. "
91                            + context.getCurrentTemplateName() + " [line " + getLine()
92                            + ", column " + getColumn() + "]");
93  
94             return null;
95         }
96
97         return new Integer JavaDoc( ( (Integer JavaDoc) left ).intValue() - ( (Integer JavaDoc) right ).intValue() );
98     }
99 }
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