shift_action.java

package java_cup ;


/**
 * This class represents a shift action within the parse table. The action
 * simply stores the state that it shifts to and responds to queries about its
 * type.
 * 
 * @version last updated: 11/25/95
 * @author Scott Hudson
 */
public class shift_action extends parse_action
{
  /*-----------------------------------------------------------*/
  /*--- Constructor(s) ----------------------------------------*/
  /*-----------------------------------------------------------*/
  /**
   * Simple constructor.
   * 
   * @param shft_to the state that this action shifts to.
   */
  public shift_action ( lalr_state shft_to ) throws internal_error
  {
    /* sanity check */
    if ( shft_to == null )
      throw new internal_error (
          "Attempt to create a shift_action to a null state" ) ;
    _shift_to = shft_to ;
  }


  /*-----------------------------------------------------------*/
  /*--- (Access to) Instance Variables ------------------------*/
  /*-----------------------------------------------------------*/
  /** The state we shift to. */
  protected lalr_state _shift_to ;


  /** The state we shift to. */
  public lalr_state shift_to ( )
  {
    return _shift_to ;
  }


  /*-----------------------------------------------------------*/
  /*--- General Methods ---------------------------------------*/
  /*-----------------------------------------------------------*/
  /** Quick access to type of action. */
  public int kind ( )
  {
    return SHIFT ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Equality test. */
  public boolean equals ( shift_action other )
  {
    return other != null && other.shift_to ( ) == shift_to ( ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Generic equality test. */
  public boolean equals ( Object other )
  {
    if ( other instanceof shift_action )
      return equals ( ( shift_action ) other ) ;
    else return false ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Compute a hash code. */
  public int hashCode ( )
  {
    /* use the hash code of the state we are shifting to */
    return shift_to ( ).hashCode ( ) ;
  }


  /* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */
  /** Convert to a string. */
  public String toString ( )
  {
    return "SHIFT(to state " + shift_to ( ).index ( ) + ")" ;
  }
  /*-----------------------------------------------------------*/
}