/*
 [The "BSD license"]
 Copyright (c) 2005-2009 Terence Parr
 All rights reserved.

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 modification, are permitted provided that the following conditions
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 1. Redistributions of source code must retain the above copyright
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 2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
 3. The name of the author may not be used to endorse or promote products
     derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 */
package org.antlr.runtime;

A source of tokens must provide a sequence of tokens via nextToken()
 and also must reveal it's source of characters; CommonToken's text is
 computed from a CharStream; it only store indices into the char stream.
 Errors from the lexer are never passed to the parser.  Either you want
 to keep going or you do not upon token recognition error.  If you do not
 want to continue lexing then you do not want to continue parsing.  Just
 throw an exception not under RecognitionException and Java will naturally
 toss you all the way out of the recognizers.  If you want to continue
 lexing then you should not throw an exception to the parser--it has already
 requested a token.  Keep lexing until you get a valid one.  Just report
 errors and keep going, looking for a valid token.
/** A source of tokens must provide a sequence of tokens via nextToken()
 *  and also must reveal it's source of characters; CommonToken's text is
 *  computed from a CharStream; it only store indices into the char stream.
 *
 *  Errors from the lexer are never passed to the parser.  Either you want
 *  to keep going or you do not upon token recognition error.  If you do not
 *  want to continue lexing then you do not want to continue parsing.  Just
 *  throw an exception not under RecognitionException and Java will naturally
 *  toss you all the way out of the recognizers.  If you want to continue
 *  lexing then you should not throw an exception to the parser--it has already
 *  requested a token.  Keep lexing until you get a valid one.  Just report
 *  errors and keep going, looking for a valid token.
 */
public interface TokenSource {
	
Return a Token object from your input stream (usually a CharStream).
 Do not fail/return upon lexing error; keep chewing on the characters
 until you get a good one; errors are not passed through to the parser.
/** Return a Token object from your input stream (usually a CharStream).
	 *  Do not fail/return upon lexing error; keep chewing on the characters
	 *  until you get a good one; errors are not passed through to the parser.
	 */
	public Token nextToken();

	
Where are you getting tokens from? normally the implication will simply
 ask lexers input stream.
/** Where are you getting tokens from? normally the implication will simply
	 *  ask lexers input stream.
	 */
	public String getSourceName();
}