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Java > Open Source Codes > persistence > antlr > GrammarAnalyzer


1 package persistence.antlr;
2
3 /* ANTLR Translator Generator
4  * Project led by Terence Parr at http://www.jGuru.com
5  * Software rights: http://www.antlr.org/license.html
6  *
7  */
8
9 /**A GrammarAnalyzer computes lookahead from Grammar (which contains
10  * a grammar symbol table) and can then answer questions about the
11  * grammar.
12  *
13  * To access the RuleBlock for a rule name, the grammar symbol table
14  * is consulted.
15  *
16  * There should be no distinction between static & dynamic analysis.
17  * In other words, some of the easy analysis can be done statically
18  * and then the part that is hard statically can be deferred to
19  * parse-time. Interestingly, computing LL(k) for k>1 lookahead
20  * statically is O(|T|^k) where T is the grammar vocabulary, but,
21  * is O(k) at run-time (ignoring the large constant associated with
22  * the size of the grammar). In English, the difference can be
23  * described as "find the set of all possible k-sequences of input"
24  * versus "does this specific k-sequence match?".
25  */
26 public interface GrammarAnalyzer {
27     /**The epsilon token type is an imaginary type used
28      * during analysis. It indicates an incomplete look() computation.
29      * Must be kept consistent with Token constants to be between
30      * MIN_USER_TYPE and INVALID_TYPE.
31      */
32     // public static final int EPSILON_TYPE = 2;
33 public static final int NONDETERMINISTIC = Integer.MAX_VALUE; // lookahead depth
34 public static final int LOOKAHEAD_DEPTH_INIT = -1;
35 }
36
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