Resolver


1   /*
2   // $Id: //open/mondrian/src/main/mondrian/olap/fun/Resolver.java#13 $
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) 2002-2002 Kana Software, Inc.
7   // Copyright (C) 2002-2006 Julian Hyde and others
8   // All Rights Reserved.
9   // You must accept the terms of that agreement to use this software.
10  //
11  // jhyde, 3 March, 2002
12  */
13  package mondrian.olap.fun;
14  
15  import mondrian.olap.*;
16  
17  /**
18   * A <code>Resolver</code> converts a function name, invocation type, and set
19   * of arguments into a {@link FunDef}.
20   *
21   * @author jhyde
22   * @since 3 March, 2002
23   * @version $Id: //open/mondrian/src/main/mondrian/olap/fun/Resolver.java#13 $
24   */
25  public interface Resolver {
26      /**
27       * Returns the name of the function or operator.
28       */
29      String   getName();
30  
31      /**
32       * Returns the description of the function or operator.
33       */
34      String   getDescription();
35  
36      /**
37       * Returns the syntax with which the function or operator was invoked.
38       */
39      Syntax getSyntax();
40  
41      /**
42       * Given a particular set of arguments the function is applied to, returns
43       * the correct overloaded form of the function.
44       *
45       * <p>The method must increment <code>conversionCount</code> argument every
46       * time it performs an implicit type-conversion. If there are several
47       * candidate functions with the same signature, the validator will choose
48       * the one which used the fewest implicit conversions.
49       *
50       * @param args Expressions which this function call is applied to.
51       * @param validator Validator
52       * @param conversionCount This argument must be an  <code>int</code> array
53       *   with a single element; in effect, it is an in/out parameter. It
54       *   The method increments the count every time it performs a conversion.
55       *
56       * @return The function definition which matches these arguments, or null
57       *   if no function definition that this resolver knows about matches.
58       */
59      FunDef resolve(Exp[] args, Validator validator, int[] conversionCount);
60  
61      /**
62       * Returns whether a particular argument must be a scalar expression.
63       * Returns <code>false</code> if any of the variants of this resolver
64       * allows a set as its <code>k</code>th argument; true otherwise.
65       */
66      boolean requiresExpression(int k);
67  
68      /**
69       * Returns an array of symbolic constants which can appear as arguments
70       * to this function.
71       *
72       * <p>For example, the <code>DrilldownMember</code> may take the symbol
73       * <code>RECURSIVE</code> as an argument. Most functions do not define
74       * any symbolic constants.
75       *
76       * @return An array of the names of the symbolic constants
77       */
78      String  [] getReservedWords();
79  
80      /**
81       * Returns a string describing the syntax of this function, for example
82       * <pre><code>StrToSet(<String Expression>)</code></pre>
83       */
84      String   getSignature();
85  
86      /**
87       * Returns a representative example of the function which this Resolver
88       * can produce, for purposes of describing the function set. May return
89       * null if there is no representative function, or if the Resolver has
90       * a way to describe itself in more detail.
91       */
92      FunDef getFunDef();
93  }
94  
95  // End Resolver.java
96
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