shift_action


1   
2   package com.sun.java_cup.internal;
3   
4   /** This class represents a shift action within the parse table. 
5    *  The action simply stores the state that it shifts to and responds 
6    *  to queries about its type.
7    *
8    * @version last updated: 11/25/95
9    * @author  Scott Hudson
10   */
11  public class shift_action extends parse_action {
12  
13    /*-----------------------------------------------------------*/
14    /*--- Constructor(s) ----------------------------------------*/
15    /*-----------------------------------------------------------*/
16  
17    /** Simple constructor. 
18     * @param shft_to the state that this action shifts to.
19     */
20    public shift_action(lalr_state shft_to) throws internal_error
21      {
22        /* sanity check */
23        if (shft_to == null)
24      throw new internal_error(
25        "Attempt to create a shift_action to a null state");
26  
27        _shift_to = shft_to;
28      }
29  
30    /*-----------------------------------------------------------*/
31    /*--- (Access to) Instance Variables ------------------------*/
32    /*-----------------------------------------------------------*/
33  
34    /** The state we shift to. */
35    protected lalr_state _shift_to;
36  
37    /** The state we shift to. */
38    public lalr_state shift_to() {return _shift_to;}
39  
40    /*-----------------------------------------------------------*/
41    /*--- General Methods ---------------------------------------*/
42    /*-----------------------------------------------------------*/
43  
44    /** Quick access to type of action. */
45    public int kind() {return SHIFT;}
46  
47    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
48  
49    /** Equality test. */
50    public boolean equals(shift_action other)
51      {
52        return other != null && other.shift_to() == shift_to();
53      }
54  
55    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
56  
57    /** Generic equality test. */
58    public boolean equals(Object   other)
59      {
60        if (other instanceof shift_action)
61      return equals((shift_action)other);
62        else
63         return false;
64      }
65  
66    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
67  
68    /** Compute a hash code. */
69    public int hashCode()
70      {
71        /* use the hash code of the state we are shifting to */
72        return shift_to().hashCode();
73      }
74  
75    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
76  
77    /** Convert to a string. */
78    public String   toString() {return "SHIFT(to state " + shift_to().index() + ")";}
79  
80    /*-----------------------------------------------------------*/
81  
82  }
83
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