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      1 package java_cup;
      2 
      3 /** This class represents a part of a production which is a symbol (terminal
      4  *  or non terminal).  This simply maintains a reference to the symbol in
      5  *  question.
      6  *
      7  * @see     java_cup.production
      8  * @version last updated: 11/25/95
      9  * @author  Scott Hudson
     10  */
     11 public class symbol_part extends production_part {
     12 
     13   /*-----------------------------------------------------------*/
     14   /*--- Constructor(s) ----------------------------------------*/
     15   /*-----------------------------------------------------------*/
     16 
     17   /** Full constructor.
     18    * @param sym the symbol that this part is made up of.
     19    * @param lab an optional label string for the part.
     20    */
     21   public symbol_part(symbol sym, String lab) throws internal_error
     22     {
     23       super(lab);
     24 
     25       if (sym == null)
     26     throw new internal_error(
     27       "Attempt to construct a symbol_part with a null symbol");
     28       _the_symbol = sym;
     29     }
     30 
     31   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     32 
     33   /** Constructor with no label.
     34    * @param sym the symbol that this part is made up of.
     35    */
     36   public symbol_part(symbol sym) throws internal_error
     37     {
     38       this(sym,null);
     39     }
     40 
     41   /*-----------------------------------------------------------*/
     42   /*--- (Access to) Instance Variables ------------------------*/
     43   /*-----------------------------------------------------------*/
     44 
     45   /** The symbol that this part is made up of. */
     46   protected symbol _the_symbol;
     47 
     48   /** The symbol that this part is made up of. */
     49   public symbol the_symbol() {return _the_symbol;}
     50 
     51   /*-----------------------------------------------------------*/
     52   /*--- General Methods ---------------------------------------*/
     53   /*-----------------------------------------------------------*/
     54 
     55   /** Respond that we are not an action part. */
     56   public boolean is_action() { return false; }
     57 
     58   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     59 
     60   /** Equality comparison. */
     61   public boolean equals(symbol_part other)
     62     {
     63       return other != null && super.equals(other) &&
     64          the_symbol().equals(other.the_symbol());
     65     }
     66 
     67   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     68 
     69   /** Generic equality comparison. */
     70   public boolean equals(Object other)
     71     {
     72       if (!(other instanceof symbol_part))
     73     return false;
     74       else
     75     return equals((symbol_part)other);
     76     }
     77 
     78   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     79 
     80   /** Produce a hash code. */
     81   public int hashCode()
     82     {
     83       return super.hashCode() ^
     84          (the_symbol()==null ? 0 : the_symbol().hashCode());
     85     }
     86 
     87   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     88 
     89   /** Convert to a string. */
     90   public String toString()
     91     {
     92       if (the_symbol() != null)
     93     return super.toString() + the_symbol();
     94       else
     95     return super.toString() + "$$MISSING-SYMBOL$$";
     96     }
     97 
     98   /*-----------------------------------------------------------*/
     99 
    100 };
    101