KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > java_cup > runtime > Symbol


1 package java_cup.runtime;
2
3 /**
4  * Defines the Symbol class, which is used to represent all terminals
5  * and nonterminals while parsing. The lexer should pass CUP Symbols
6  * and CUP returns a Symbol.
7  *
8  * @version last updated: 7/3/96
9  * @author Frank Flannery
10  */
11
12 /* ****************************************************************
13   Class Symbol
14   what the parser expects to receive from the lexer.
15   the token is identified as follows:
16   sym: the symbol type
17   parse_state: the parse state.
18   value: is the lexical value of type Object
19   left : is the left position in the original input file
20   right: is the right position in the original input file
21 ******************************************************************/
22
23 public class Symbol {
24
25 /*******************************
26   Constructor for l,r values
27  *******************************/
28
29   public Symbol(int id, int l, int r, Object JavaDoc o) {
30     this(id);
31     left = l;
32     right = r;
33     value = o;
34   }
35
36 /*******************************
37   Constructor for no l,r values
38 ********************************/
39
40   public Symbol(int id, Object JavaDoc o) {
41     this(id, -1, -1, o);
42   }
43
44 /*****************************
45   Constructor for no value
46   ***************************/
47
48   public Symbol(int id, int l, int r) {
49     this(id, l, r, null);
50   }
51
52 /***********************************
53   Constructor for no value or l,r
54 ***********************************/
55
56   public Symbol(int sym_num) {
57     this(sym_num, -1);
58     left = -1;
59     right = -1;
60     value = null;
61   }
62
63 /***********************************
64   Constructor to give a start state
65 ***********************************/
66   Symbol(int sym_num, int state)
67     {
68       sym = sym_num;
69       parse_state = state;
70     }
71
72 /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
73
74   /** The symbol number of the terminal or non terminal being represented */
75   public int sym;
76
77   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
78
79   /** The parse state to be recorded on the parse stack with this symbol.
80    * This field is for the convenience of the parser and shouldn't be
81    * modified except by the parser.
82    */
83   public int parse_state;
84   /** This allows us to catch some errors caused by scanners recycling
85    * symbols. For the use of the parser only. [CSA, 23-Jul-1999] */
86   boolean used_by_parser = false;
87
88 /*******************************
89   The data passed to parser
90  *******************************/
91
92   public int left, right;
93   public Object JavaDoc value;
94
95   /*****************************
96     Printing this token out. (Override for pretty-print).
97     ****************************/
98   public String JavaDoc toString() { return "#"+sym; }
99 }
100
101
102
103
104
105
106
Popular Tags