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Java > Open Source Codes > mondrian > olap > Exp


1 /*
2 // $Id: //open/mondrian/src/main/mondrian/olap/Exp.java#19 $
3 // This software is subject to the terms of the Common Public License
4 // Agreement, available at the following URL:
5 // http://www.opensource.org/licenses/cpl.html.
6 // Copyright (C) 1999-2002 Kana Software, Inc.
7 // Copyright (C) 2001-2006 Julian Hyde and others
8 // All Rights Reserved.
9 // You must accept the terms of that agreement to use this software.
10 //
11 // jhyde, 20 January, 1999
12 */
13
14 package mondrian.olap;
15
16 import mondrian.olap.type.Type;
17 import mondrian.calc.Calc;
18 import mondrian.calc.ExpCompiler;
19 import mondrian.mdx.MdxVisitorImpl;
20 import mondrian.mdx.MdxVisitor;
21
22 import java.io.PrintWriter JavaDoc;
23
24 /**
25  * An <code>Exp</code> is an MDX expression.
26  *
27  * @author jhyde
28  * @since 1.0
29  * @version $Id: //open/mondrian/src/main/mondrian/olap/Exp.java#19 $
30  */
31 public interface Exp {
32
33     Exp clone();
34
35     /**
36      * Returns the {@link Category} of the expression.
37      *
38      * @post Category.instance().isValid(return)
39      */
40     int getCategory();
41
42     /**
43      * Returns the type of this expression. Never null.
44      */
45     Type getType();
46
47     /**
48      * Writes the MDX representation of this expression to a print writer.
49      * Sub-expressions are invoked recursively.
50      *
51      * @param pw PrintWriter
52      */
53     void unparse(PrintWriter JavaDoc pw);
54
55     /**
56      * Validates this expression.
57      *
58      * The validator acts in the role of 'visitor' (see Gang of Four
59      * 'visitor pattern'), and an expression in the role of 'visitee'.
60      *
61      * @param validator Validator contains validation context
62      *
63      * @return The validated expression; often but not always the same as
64      * this expression
65      */
66     Exp accept(Validator validator);
67
68     /**
69      * Converts this expression into an a tree of expressions which can be
70      * efficiently evaluated.
71      *
72      * @param compiler
73      * @return A compiled expression
74      */
75     Calc accept(ExpCompiler compiler);
76
77     /**
78      * Accepts a visitor to this Exp.
79      * The implementation should generally dispatches to the
80      * {@link MdxVisitor#visit} method appropriate to the type of expression.
81      *
82      * @param visitor Visitor
83      */
84     Object JavaDoc accept(MdxVisitor visitor);
85 }
86
87 // End Exp.java
88
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