KickJava   Java API By Example, From Geeks To Geeks.

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


1
2 package com.sun.java_cup.internal;
3
4 /** This class represents one row (corresponding to one machine state) of the
5  * parse action table.
6  */
7 public class parse_action_row {
8
9   /*-----------------------------------------------------------*/
10   /*--- Constructor(s) ----------------------------------------*/
11   /*-----------------------------------------------------------*/
12            
13   /** Simple constructor. Note: this should not be used until the number of
14    * terminals in the grammar has been established.
15    */
16   public parse_action_row()
17     {
18       /* make sure the size is set */
19       if (_size <= 0 ) _size = terminal.number();
20
21       /* allocate the array */
22       under_term = new parse_action[size()];
23
24       /* set each element to an error action */
25       for (int i=0; i<_size; i++)
26     under_term[i] = new parse_action();
27     }
28
29   /*-----------------------------------------------------------*/
30   /*--- (Access to) Static (Class) Variables ------------------*/
31   /*-----------------------------------------------------------*/
32
33   /** Number of columns (terminals) in every row. */
34   protected static int _size = 0;
35
36   /** Number of columns (terminals) in every row. */
37   public static int size() {return _size;}
38
39   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
40
41   /** Table of reduction counts (reused by compute_default()). */
42   protected static int reduction_count[] = null;
43
44   /*-----------------------------------------------------------*/
45   /*--- (Access to) Instance Variables ------------------------*/
46   /*-----------------------------------------------------------*/
47
48   /** Actual action entries for the row. */
49   public parse_action under_term[];
50
51   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
52
53   /** Default (reduce) action for this row. -1 will represent default
54    * of error.
55    */
56   public int default_reduce;
57
58   /*-----------------------------------------------------------*/
59   /*--- General Methods ---------------------------------------*/
60   /*-----------------------------------------------------------*/
61     
62   /** Compute the default (reduce) action for this row and store it in
63    * default_reduce. In the case of non-zero default we will have the
64    * effect of replacing all errors by that reduction. This may cause
65    * us to do erroneous reduces, but will never cause us to shift past
66    * the point of the error and never cause an incorrect parse. -1 will
67    * be used to encode the fact that no reduction can be used as a
68    * default (in which case error will be used).
69    */
70   public void compute_default()
71     {
72       int i, prod, max_prod, max_red;
73
74       /* if we haven't allocated the count table, do so now */
75       if (reduction_count == null)
76     reduction_count = new int[production.number()];
77
78       /* clear the reduction count table and maximums */
79       for (i = 0; i < production.number(); i++)
80     reduction_count[i] = 0;
81       max_prod = -1;
82       max_red = 0;
83      
84       /* walk down the row and look at the reduces */
85       for (i = 0; i < size(); i++)
86     if (under_term[i].kind() == parse_action.REDUCE)
87       {
88         /* count the reduce in the proper production slot and keep the
89            max up to date */
90         prod = ((reduce_action)under_term[i]).reduce_with().index();
91         reduction_count[prod]++;
92         if (reduction_count[prod] > max_red)
93           {
94         max_red = reduction_count[prod];
95         max_prod = prod;
96           }
97       }
98
99        /* record the max as the default (or -1 for not found) */
100        default_reduce = max_prod;
101     }
102
103   /*-----------------------------------------------------------*/
104
105 }
106
107
Popular Tags