terminal.java

package java_cup ;


import java.util.Enumeration ;
import java.util.Hashtable ;


/**
 * This class represents a terminal symbol in the grammar. Each terminal has a
 * textual name, an index, and a string which indicates the type of object it
 * will be implemented with at runtime (i.e. the class of object that will be
 * returned by the scanner and pushed on the parse stack to represent it).
 * 
 * @version last updated: 7/3/96
 * @author Frank Flannery
 */
public class terminal extends symbol
{
  /*-----------------------------------------------------------*/
  /*--- Constructor(s) ----------------------------------------*/
  /*-----------------------------------------------------------*/
  /**
   * Full constructor.
   * 
   * @param nm the name of the terminal.
   * @param tp the type of the terminal.
   */
  public terminal ( String nm , String tp , int precedence_side ,
      int precedence_num )
  {
    /* superclass does most of the work */
    super ( nm , tp ) ;
    /* add to set of all terminals and check for duplicates */
    Object conflict = _all.put ( nm , this ) ;
    if ( conflict != null )
    // can't throw an execption here because this is used in static
      // initializers, so we do a crash instead
      // was:
      // throw new internal_error("Duplicate terminal (" + nm + ") created");
      ( new internal_error ( "Duplicate terminal (" + nm + ") created" ) )
          .crash ( ) ;
    /* assign a unique index */
    _index = next_index ++ ;
    /* set the precedence */
    _precedence_num = precedence_num ;
    _precedence_side = precedence_side ;
    /* add to by_index set */
    _all_by_index.put ( new Integer ( _index ) , this ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /**
   * Constructor for non-precedented terminal
   */
  public terminal ( String nm , String tp )
  {
    this ( nm , tp , assoc.no_prec , - 1 ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /**
   * Constructor with default type.
   * 
   * @param nm the name of the terminal.
   */
  public terminal ( String nm )
  {
    this ( nm , null ) ;
  }


  /*-----------------------------------------------------------*/
  /*-------------------  Class Variables  ---------------------*/
  /*-----------------------------------------------------------*/
  private int _precedence_num ;


  private int _precedence_side ;


  /*-----------------------------------------------------------*/
  /*--- (Access to) Static (Class) Variables ------------------*/
  /*-----------------------------------------------------------*/
  /**
   * Table of all terminals. Elements are stored using name strings as the key
   */
  protected static Hashtable _all = new Hashtable ( ) ;


  // Hm Added clear to clear all static fields
  public static void clear ( )
  {
    _all.clear ( ) ;
    _all_by_index.clear ( ) ;
    next_index = 0 ;
    EOF = new terminal ( "EOF" ) ;
    error = new terminal ( "error" ) ;
  }


  /** Access to all terminals. */
  public static Enumeration all ( )
  {
    return _all.elements ( ) ;
  }


  /** Lookup a terminal by name string. */
  public static terminal find ( String with_name )
  {
    if ( with_name == null )
      return null ;
    else return ( terminal ) _all.get ( with_name ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Table of all terminals indexed by their index number. */
  protected static Hashtable _all_by_index = new Hashtable ( ) ;


  /** Lookup a terminal by index. */
  public static terminal find ( int indx )
  {
    Integer the_indx = new Integer ( indx ) ;
    return ( terminal ) _all_by_index.get ( the_indx ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Total number of terminals. */
  public static int number ( )
  {
    return _all.size ( ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Static counter to assign unique index. */
  protected static int next_index = 0 ;


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Special terminal for end of input. */
  public static terminal EOF = new terminal ( "EOF" ) ;


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** special terminal used for error recovery */
  public static terminal error = new terminal ( "error" ) ;


  /*-----------------------------------------------------------*/
  /*--- General Methods ---------------------------------------*/
  /*-----------------------------------------------------------*/
  /** Report this symbol as not being a non-terminal. */
  public boolean is_non_term ( )
  {
    return false ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Convert to a string. */
  public String toString ( )
  {
    return super.toString ( ) + "[" + index ( ) + "]" ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** get the precedence of a terminal */
  public int precedence_num ( )
  {
    return _precedence_num ;
  }


  public int precedence_side ( )
  {
    return _precedence_side ;
  }


  /** set the precedence of a terminal */
  public void set_precedence ( int p , int new_prec )
  {
    _precedence_side = p ;
    _precedence_num = new_prec ;
  }
  /*-----------------------------------------------------------*/
}