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Symbol.java

package java_cup.runtime;

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Bandera, a Java(TM) analysis and transformation toolkit           *
 * Copyright (C) 1998-2001 SAnToS Laboratories (santos@cis.ksu.edu)  *

 * All rights reserved.                                              *
 *                                                                   *
 * This work was done as a project in the SAnToS Laboratory,         *
 * Department of Computing and Information Sciences, Kansas State    *
 * University, USA (http://www.cis.ksu.edu/santos).                  *
 * It is understood that any modification not identified as such is  *
 * not covered by the preceding statement.                           *
 *                                                                   *
 * This work is free software; you can redistribute it and/or        *
 * modify it under the terms of the GNU Library General Public       *
 * License as published by the Free Software Foundation; either      *
 * version 2 of the License, or (at your option) any later version.  *
 *                                                                   *
 * This work is distributed in the hope that it will be useful,      *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of    *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU *
 * Library General Public License for more details.                  *
 *                                                                   *
 * You should have received a copy of the GNU Library General Public *
 * License along with this toolkit; if not, write to the             *
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,      *
 * Boston, MA  02111-1307, USA.                                      *
 *                                                                   *
 * Java is a trademark of Sun Microsystems, Inc.                     *
 *                                                                   *
 * To submit a bug report, send a comment, or get the latest news on *
 * this project and other SAnToS projects, please visit the web-site *
 *                http://www.cis.ksu.edu/santos                      *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/**
 * Defines the Symbol class, which is used to represent all terminals
 * and nonterminals while parsing.  The lexer should pass CUP Symbols 
 * and CUP returns a Symbol.
 *
 * @version last updated: 7/3/96
 * @author  Frank Flannery
 */

/* ****************************************************************
  Class Symbol
  what the parser expects to receive from the lexer. 
  the token is identified as follows:
  sym:    the symbol type
  parse_state: the parse state.
  value:  is the lexical value of type Object
  left :  is the left position in the original input file
  right:  is the right position in the original input file
******************************************************************/

public class Symbol {

/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** The symbol number of the terminal or non terminal being represented */
  public int sym;

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** The parse state to be recorded on the parse stack with this symbol.
   *  This field is for the convenience of the parser and shouldn't be 
   *  modified except by the parser. 
   */
  public int parse_state;
  /** This allows us to catch some errors caused by scanners recycling
   *  symbols.  For the use of the parser only. [CSA, 23-Jul-1999] */
  boolean used_by_parser = false;

/*******************************
  The data passed to parser
 *******************************/

  public int left, right;
  public Object value;

/***********************************
  Constructor for no value or l,r
***********************************/

  public Symbol(int sym_num) {
    this(sym_num, -1);
    left = -1;
    right = -1;
    value = null;
  }  
/***********************************
  Constructor to give a start state
***********************************/
  Symbol(int sym_num, int state)
    {
      sym = sym_num;
      parse_state = state;
    }
/*****************************
  Constructor for no value
  ***************************/

  public Symbol(int id, int l, int r) {
    this(id, l, r, null);
  }  
/*******************************
  Constructor for l,r values
 *******************************/

  public Symbol(int id, int l, int r, Object o) {
    this(id);
    left = l;
    right = r;
    value = o;
  }  
/*******************************
  Constructor for no l,r values
********************************/

  public Symbol(int id, Object o) {
    this(id, -1, -1, o);
  }  
  /*****************************
    Printing this token out. (Override for pretty-print).
    ****************************/
  public String toString() { return "#"+sym; }  
}

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