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    */
shift_action(lalr_state shft_to)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. */
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. */
kind()45   public int kind() {return SHIFT;}
46 
47   /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
48 
49   /** Equality test. */
equals(shift_action other)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. */
equals(Object other)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. */
hashCode()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. */
toString()78   public String toString() {return "SHIFT(" + shift_to().index() + ")";}
79 
80   /*-----------------------------------------------------------*/
81 
82 };
83