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
 */
@SuppressWarnings (
{ "all", "unchecked" } )
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;
  }
  /*-----------------------------------------------------------*/
}