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      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 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(" + shift_to().index() + ")";}
     79 
     80   /*-----------------------------------------------------------*/
     81 
     82 };
     83