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Java > Open Source Codes > com > sun > java_cup > internal > symbol_part


1 package com.sun.java_cup.internal;
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 com.sun.java_cup.internal.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 JavaDoc 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 JavaDoc 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 JavaDoc 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
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