grammaranalyzer.java

来自「SRI international 发布的OAA框架软件」· Java 代码 · 共 37 行

package antlr_oaa;

/* ANTLR Translator Generator
 * Project led by Terence Parr at http://www.jGuru.com
 * Software rights: http://www.antlr.org/RIGHTS.html
 *
 * $Id: GrammarAnalyzer.java,v 1.1 2002/11/08 17:38:02 agno Exp $
 */

/**A GrammarAnalyzer computes lookahead from Grammar (which contains
 * a grammar symbol table) and can then answer questions about the
 * grammar.
 *
 * To access the RuleBlock for a rule name, the grammar symbol table
 * is consulted.
 *
 * There should be no distinction between static & dynamic analysis.
 * In other words, some of the easy analysis can be done statically
 * and then the part that is hard statically can be deferred to
 * parse-time.  Interestingly, computing LL(k) for k>1 lookahead
 * statically is O(|T|^k) where T is the grammar vocabulary, but,
 * is O(k) at run-time (ignoring the large constant associated with
 * the size of the grammar).  In English, the difference can be
 * described as "find the set of all possible k-sequences of input"
 * versus "does this specific k-sequence match?".
 */
public interface GrammarAnalyzer {
	/**The epsilon token type is an imaginary type used 
	 * during analysis.  It indicates an incomplete look() computation.
	 * Must be kept consistent with Token constants to be between
	 * MIN_USER_TYPE and INVALID_TYPE.
	 */
	// public static final int EPSILON_TYPE = 2;
	public static final int NONDETERMINISTIC = Integer.MAX_VALUE; // lookahead depth
	public static final int LOOKAHEAD_DEPTH_INIT = -1;
}