KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > com > quadcap > sql > Expression


1 package com.quadcap.sql;
2
3 /* Copyright 1999 - 2003 Quadcap Software. All rights reserved.
4  *
5  * This software is distributed under the Quadcap Free Software License.
6  * This software may be used or modified for any purpose, personal or
7  * commercial. Open Source redistributions are permitted. Commercial
8  * redistribution of larger works derived from, or works which bundle
9  * this software requires a "Commercial Redistribution License"; see
10  * http://www.quadcap.com/purchase.
11  *
12  * Redistributions qualify as "Open Source" under one of the following terms:
13  *
14  * Redistributions are made at no charge beyond the reasonable cost of
15  * materials and delivery.
16  *
17  * Redistributions are accompanied by a copy of the Source Code or by an
18  * irrevocable offer to provide a copy of the Source Code for up to three
19  * years at the cost of materials and delivery. Such redistributions
20  * must allow further use, modification, and redistribution of the Source
21  * Code under substantially the same terms as this license.
22  *
23  * Redistributions of source code must retain the copyright notices as they
24  * appear in each source code file, these license terms, and the
25  * disclaimer/limitation of liability set forth as paragraph 6 below.
26  *
27  * Redistributions in binary form must reproduce this Copyright Notice,
28  * these license terms, and the disclaimer/limitation of liability set
29  * forth as paragraph 6 below, in the documentation and/or other materials
30  * provided with the distribution.
31  *
32  * The Software is provided on an "AS IS" basis. No warranty is
33  * provided that the Software is free of defects, or fit for a
34  * particular purpose.
35  *
36  * Limitation of Liability. Quadcap Software shall not be liable
37  * for any damages suffered by the Licensee or any third party resulting
38  * from use of the Software.
39  */
40
41 import java.io.IOException JavaDoc;
42
43 import java.util.Enumeration JavaDoc;
44 import java.util.Vector JavaDoc;
45
46 import java.sql.SQLException JavaDoc;
47
48 import com.quadcap.sql.types.Op;
49 import com.quadcap.sql.types.Type;
50 import com.quadcap.sql.types.Value;
51
52 import com.quadcap.util.Debug;
53
54 /**
55  * Base class for all expression types.
56  *
57  * @author Stan Bailes
58  */
59
60 public abstract class Expression {
61     /**
62      * Returns zero if this is a scalar expression, one if it's a vector
63      * type and 2 if it's a table/cursor type.
64      */
65     public abstract int rank();
66
67     /**
68      * Return the expression's type if known
69      */
70     public abstract Type getType(Session session, Cursor cursor)
71         throws SQLException JavaDoc;
72
73     /**
74      * If this is a scalar, return its value
75      */
76     public Value getValue(Session session, Cursor cursor)
77         throws SQLException JavaDoc
78     {
79         return null;
80     }
81
82     /**
83      * If this is a vector, return the value
84      */
85     public Row getValues(Session session, Cursor cursor) throws SQLException JavaDoc {
86     if (rank() == 0) {
87         Value v = getValue(session, cursor);
88         Row row = new Row(1);
89         row.set(1, v);
90         return row;
91     } else {
92         throw new SQLException JavaDoc("getValues, rank = " + rank(), "Q0000");
93     }
94     }
95
96     /**
97      * If this is a cursor, return the value
98      */
99     public Cursor getCursor(Session session, Cursor cursor)
100         throws SQLException JavaDoc
101     {
102     return null;
103     }
104
105     /**
106      * Negate the logical value of the expression
107      */
108     public void invert() throws antlr.RecognitionException {
109         throw new antlr.RecognitionException("Error, not a boolean expression");
110     }
111
112     /**
113      * Give a visitor access to the parse tree.
114      */
115     public void visitSubExpressions(ExpressionVisitor v) {}
116
117
118     public String JavaDoc getName() { return null; }
119
120     abstract public String JavaDoc toString();
121     
122 }
123
Popular Tags