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Java > Open Source Codes > mondrian > calc > TupleCalc


1 /*
2 // $Id: //open/mondrian/src/main/mondrian/calc/TupleCalc.java#5 $
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) 2006-2007 Julian Hyde
7 // All Rights Reserved.
8 // You must accept the terms of that agreement to use this software.
9 */
10 package mondrian.calc;
11
12 import mondrian.olap.Member;
13 import mondrian.olap.Evaluator;
14
15 /**
16  * Expression which yields a tuple.
17  *
18  * <p>The tuple is represented as an array of {@link Member} objects,
19  * <code>null</code> to represent the null tuple.
20  *
21  * <p>When implementing this interface, it is convenient to extend
22  * {@link mondrian.calc.impl.AbstractTupleCalc}, but it is not required.
23  *
24  * @author jhyde
25  * @version $Id: //open/mondrian/src/main/mondrian/calc/TupleCalc.java#5 $
26  * @since Sep 27, 2005
27  */
28 public interface TupleCalc extends Calc {
29     /**
30      * Evaluates this expression to yield a tuple.
31      *
32      * <p>A tuple cannot contain any null members. If any of the members is
33      * null, this method must return a null.
34      *
35      * @post result == null || !tupleContainsNullMember(result)
36      *
37      * @param evaluator Evaluation context
38      * @return an array of members, or null to represent the null tuple
39      */
40     Member[] evaluateTuple(Evaluator evaluator);
41 }
42
43 // End TupleCalc.java
44
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