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      1 package java_cup;
      2 
      3 /** This abstract class serves as the base class for grammar symbols (i.e.,
      4  * both terminals and non-terminals).  Each symbol has a name string, and
      5  * a string giving the type of object that the symbol will be represented by
      6  * on the runtime parse stack.  In addition, each symbol maintains a use count
      7  * in order to detect symbols that are declared but never used, and an index
      8  * number that indicates where it appears in parse tables (index numbers are
      9  * unique within terminals or non terminals, but not across both).
     10  *
     11  * @see     java_cup.terminal
     12  * @see     java_cup.non_terminal
     13  * @version last updated: 11/25/95
     14  * @author  Scott Hudson
     15  */
     16 public abstract class symbol {
     17    /*-----------------------------------------------------------*/
     18    /*--- Constructor(s) ----------------------------------------*/
     19    /*-----------------------------------------------------------*/
     20 
     21    /** Full constructor.
     22     * @param nm the name of the symbol.
     23     * @param tp a string with the type name.
     24     */
     25    public symbol(String nm, String tp)
     26      {
     27        /* sanity check */
     28        if (nm == null) nm = "";
     29 
     30        /* apply default if no type given */
     31        if (tp == null) tp = "java_cup.runtime.token";
     32 
     33        _name = nm;
     34        _stack_type = tp;
     35      }
     36 
     37   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     38 
     39    /** Constructor with default type.
     40     * @param nm the name of the symbol.
     41     */
     42    public symbol(String nm)
     43      {
     44        this(nm, null);
     45      }
     46 
     47    /*-----------------------------------------------------------*/
     48    /*--- (Access to) Instance Variables ------------------------*/
     49    /*-----------------------------------------------------------*/
     50 
     51    /** String for the human readable name of the symbol. */
     52    protected String _name;
     53 
     54    /** String for the human readable name of the symbol. */
     55    public String name() {return _name;}
     56 
     57   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     58 
     59    /** String for the type of object used for the symbol on the parse stack. */
     60    protected String _stack_type;
     61 
     62    /** String for the type of object used for the symbol on the parse stack. */
     63    public String stack_type() {return _stack_type;}
     64 
     65   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     66 
     67    /** Count of how many times the symbol appears in productions. */
     68    protected int _use_count = 0;
     69 
     70    /** Count of how many times the symbol appears in productions. */
     71    public int use_count() {return _use_count;}
     72 
     73    /** Increment the use count. */
     74    public void note_use() {_use_count++;}
     75 
     76   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     77 
     78   /** Index of this symbol (terminal or non terminal) in the parse tables.
     79    *  Note: indexes are unique among terminals and unique among non terminals,
     80    *  however, a terminal may have the same index as a non-terminal, etc.
     81    */
     82    protected int _index;
     83 
     84   /** Index of this symbol (terminal or non terminal) in the parse tables.
     85    *  Note: indexes are unique among terminals and unique among non terminals,
     86    *  however, a terminal may have the same index as a non-terminal, etc.
     87    */
     88    public int index() {return _index;}
     89 
     90   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     91 
     92   /** Indicate if this is a non-terminal.  Here in the base class we
     93    *  don't know, so this is abstract.
     94    */
     95   public abstract boolean is_non_term();
     96 
     97   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
     98 
     99   /** Convert to a string. */
    100   public String toString()
    101     {
    102       return name();
    103     }
    104 
    105   /*-----------------------------------------------------------*/
    106 
    107 };
    108