symbol_part.java

package java_cup ;


/**
 * This class represents a part of a production which is a symbol (terminal or
 * non terminal). This simply maintains a reference to the symbol in question.
 * 
 * @see java_cup.production
 * @version last updated: 11/25/95
 * @author Scott Hudson
 */
public class symbol_part extends production_part
{
  /*-----------------------------------------------------------*/
  /*--- Constructor(s) ----------------------------------------*/
  /*-----------------------------------------------------------*/
  /**
   * Full constructor.
   * 
   * @param sym the symbol that this part is made up of.
   * @param lab an optional label string for the part.
   */
  public symbol_part ( symbol sym , String lab ) throws internal_error
  {
    super ( lab ) ;
    if ( sym == null )
      throw new internal_error (
          "Attempt to construct a symbol_part with a null symbol" ) ;
    _the_symbol = sym ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /**
   * Constructor with no label.
   * 
   * @param sym the symbol that this part is made up of.
   */
  public symbol_part ( symbol sym ) throws internal_error
  {
    this ( sym , null ) ;
  }


  /*-----------------------------------------------------------*/
  /*--- (Access to) Instance Variables ------------------------*/
  /*-----------------------------------------------------------*/
  /** The symbol that this part is made up of. */
  protected symbol _the_symbol ;


  /** The symbol that this part is made up of. */
  public symbol the_symbol ( )
  {
    return _the_symbol ;
  }


  /*-----------------------------------------------------------*/
  /*--- General Methods ---------------------------------------*/
  /*-----------------------------------------------------------*/
  /** Respond that we are not an action part. */
  public boolean is_action ( )
  {
    return false ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Equality comparison. */
  public boolean equals ( symbol_part other )
  {
    return other != null && super.equals ( other )
        && the_symbol ( ).equals ( other.the_symbol ( ) ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Generic equality comparison. */
  public boolean equals ( Object other )
  {
    if ( ! ( other instanceof symbol_part ) )
      return false ;
    else return equals ( ( symbol_part ) other ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Produce a hash code. */
  public int hashCode ( )
  {
    return super.hashCode ( )
        ^ ( the_symbol ( ) == null ? 0 : the_symbol ( ).hashCode ( ) ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Convert to a string. */
  public String toString ( )
  {
    if ( the_symbol ( ) != null )
      return super.toString ( ) + the_symbol ( ) ;
    else return super.toString ( ) + "$$MISSING-SYMBOL$$" ;
  }
  /*-----------------------------------------------------------*/
}