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Java > Open Source Codes > org > mr > api > jms > selector > syntax > MathOperator


1 /*
2  * Copyright 2002 by
3  * <a HREF="http://www.coridan.com">Coridan</a>
4  * <a HREF="mailto: support@coridan.com ">support@coridan.com</a>
5  *
6  * The contents of this file are subject to the Mozilla Public License Version
7  * 1.1 (the "License"); you may not use this file except in compliance with the
8  * License. You may obtain a copy of the License at
9  * http://www.mozilla.org/MPL/
10  *
11  * Software distributed under the License is distributed on an "AS IS" basis,
12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13  * for the specific language governing rights and limitations under the
14  * License.
15  *
16  * The Original Code is "MantaRay" (TM).
17  *
18  * The Initial Developer of the Original Code is Coridan.
19  * Portions created by the Initial Developer are Copyright (C) 2006
20  * Coridan Inc. All Rights Reserved.
21  *
22  * Contributor(s): all the names of the contributors are added in the source
23  * code where applicable.
24  *
25  * Alternatively, the contents of this file may be used under the terms of the
26  * LGPL license (the "GNU LESSER GENERAL PUBLIC LICENSE"), in which case the
27  * provisions of LGPL are applicable instead of those above. If you wish to
28  * allow use of your version of this file only under the terms of the LGPL
29  * License and not to allow others to use your version of this file under
30  * the MPL, indicate your decision by deleting the provisions above and
31  * replace them with the notice and other provisions required by the LGPL.
32  * If you do not delete the provisions above, a recipient may use your version
33  * of this file under either the MPL or the GNU LESSER GENERAL PUBLIC LICENSE.
34  
35  *
36  * This library is free software; you can redistribute it and/or modify it
37  * under the terms of the MPL as stated above or under the terms of the GNU
38  * Lesser General Public License as published by the Free Software Foundation;
39  * either version 2.1 of the License, or any later version.
40  *
41  * This library is distributed in the hope that it will be useful, but WITHOUT
42  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
43  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
44  * License for more details.
45  */
46 package org.mr.api.jms.selector.syntax;
47
48 import javax.jms.Message JavaDoc;
49
50
51 /**
52  * This class is the base class for all expressions that are numeric binary
53  * operators. These return a numeric result when evaluated, or null
54  * if the result is undefined.
55  *
56  */
57 abstract class MathOperator extends BinaryOperator {
58
59     /**
60      * Construct a newMathOperator
61      *
62      * @param operator the operator
63      * @param leftHand the left hand side of the expression
64      * @param rightHand the right hand side of the expression
65      */
66     protected MathOperator(final String JavaDoc operator, final Expression leftHand,final Expression rightHand) {
67         super(operator, leftHand, rightHand);
68     }//MathOperator
69
70
71     /**
72      * Evaluate the expression
73      *
74      * @param msg the message to evaluate this expression against
75      * @return the result of expression
76      * @throws TypeMismatchException if the result of the left or right hand expressions are not numeric
77      */
78     public final MantaObject evaluate(final Message JavaDoc msg) throws TypeMismatchException {
79
80         MantaNumber result = null;
81         MantaNumber leftHand = TypeCaster.castToNumber(left().evaluate(msg), context());
82         
83         if (leftHand != null) {
84             MantaNumber rightHand = TypeCaster.castToNumber(right().evaluate(msg),context());
85             if (rightHand != null) {
86                 result = evaluate(leftHand , rightHand);
87             }//if
88 }//if
89 return result;
90     }//evaluate
91
92     /**
93      * Evaluate the expression
94      *
95      * @param leftHand the left hand side of the expression
96      * @param rightHand the right hand side of the expression
97      * @return the result of expression
98      */
99     protected abstract MantaNumber evaluate(final MantaNumber leftHand, final MantaNumber rightHand);
100
101     /**
102      * The context of the expression, for error reporting purposes
103      *
104      * @return the context of the expression
105      */
106     private final String JavaDoc context() {
107         return "operator " + operator();
108     }//context
109 }//MathOperator
110
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