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     */
symbol(String nm, String tp)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     */
symbol(String nm)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. */
name()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. */
stack_type()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. */
use_count()71    public int use_count() {return _use_count;}
72 
73    /** Increment the use count. */
note_use()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    */
index()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    */
is_non_term()95   public abstract boolean is_non_term();
96 
97   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
98 
99   /** Convert to a string. */
toString()100   public String toString()
101     {
102       return name();
103     }
104 
105   /*-----------------------------------------------------------*/
106 
107 };
108