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: Alternative.java,v 1.1 2002/11/08 17:38:22 agno Exp $
 */

import java.util.Hashtable;

/** Intermediate data class holds information about an alternative */
class Alternative {
	// Tracking alternative linked list
	AlternativeElement head;   // head of alt element list
	AlternativeElement tail;  // last element added

	// Syntactic predicate block if non-null
	protected SynPredBlock synPred;
	// Semantic predicate action if non-null
	protected String semPred;
	// Exception specification if non-null
	protected ExceptionSpec exceptionSpec;
	// Init action if non-null;
	protected Lookahead[] cache;	// lookahead for alt.  Filled in by
									// deterministic() only!!!!!!!  Used for
									// code gen after calls to deterministic()
									// and used by deterministic for (...)*, (..)+,
									// and (..)? blocks.  1..k
	protected int lookaheadDepth;	// each alt has different look depth possibly.
									// depth can be NONDETERMINISTIC too.
									// 0..n-1
	// If non-null, Tree specification ala -> A B C (not implemented)
	protected Token treeSpecifier = null;
	// True of AST generation is on for this alt
	private boolean doAutoGen;


	public Alternative() {
	}
	public Alternative(AlternativeElement firstElement) {
		addElement(firstElement);
	}
	public void addElement(AlternativeElement e)
	{
		// Link the element into the list
		if ( head == null ) {
			head = tail = e;
		}
		else {
			tail.next = e;
			tail = e;
		}
	}
	public boolean atStart() { return head == null; }
	public boolean getAutoGen() { 
		// Don't build an AST if there is a tree-rewrite-specifier
		return doAutoGen && treeSpecifier == null; 
	}
	public Token getTreeSpecifier() {
		return treeSpecifier;
	}
	public void setAutoGen(boolean doAutoGen_) {
		doAutoGen = doAutoGen_;
	}
}