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Java > Open Source Codes > java_cup > shift_action


1
2 package java_cup;
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 JavaDoc 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 JavaDoc toString() {return "SHIFT(to state " + shift_to().index() + ")";}
79
80   /*-----------------------------------------------------------*/
81
82 }
83
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