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parse_action_table.java

package java_cup;

import java.util.Enumeration;

/** This class represents the complete "action" table of the parser. 
 *  It has one row for each state in the parse machine, and a column for
 *  each terminal symbol.  Each entry in the table represents a shift,
 *  reduce, or an error.  
 *
 * @see     java_cup.parse_action
 * @see     java_cup.parse_action_row
 * @version last updated: 11/25/95
 * @author  Scott Hudson
 */
00016 public class parse_action_table {

  /*-----------------------------------------------------------*/
  /*--- Constructor(s) ----------------------------------------*/
  /*-----------------------------------------------------------*/

  /** Simple constructor.  All terminals, non-terminals, and productions must 
   *  already have been entered, and the viable prefix recognizer should
   *  have been constructed before this is called.
   */
00026   public parse_action_table()
    {
      /* determine how many states we are working with */
      _num_states = lalr_state.number();

      /* allocate the array and fill it in with empty rows */
      under_state = new parse_action_row[_num_states];
      for (int i=0; i<_num_states; i++)
      under_state[i] = new parse_action_row();
    }

  /*-----------------------------------------------------------*/
  /*--- (Access to) Instance Variables ------------------------*/
  /*-----------------------------------------------------------*/

  /** How many rows/states are in the machine/table. */
00042   protected int _num_states;

  /** How many rows/states are in the machine/table. */
00045   public int num_states() {return _num_states;}

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Actual array of rows, one per state. */
00050   public  parse_action_row[] under_state;

  /*-----------------------------------------------------------*/
  /*--- General Methods ---------------------------------------*/
  /*-----------------------------------------------------------*/

  /** Check the table to ensure that all productions have been reduced. 
   *  Issue a warning message (to System.err) for each production that
   *  is never reduced.
   */
00060   public void check_reductions()
    throws internal_error
    {
      parse_action act;
      production   prod;

      /* tabulate reductions -- look at every table entry */
      for (int row = 0; row < num_states(); row++)
      {
        for (int col = 0; col < under_state[row].size(); col++)
          {
            /* look at the action entry to see if its a reduce */
            act = under_state[row].under_term[col];
            if (act != null && act.kind() == parse_action.REDUCE)
            {
              /* tell production that we used it */
              ((reduce_action)act).reduce_with().note_reduction_use();
            }
          }
      }

      /* now go across every production and make sure we hit it */
      for (Enumeration p = production.all(); p.hasMoreElements(); )
      {
        prod = (production)p.nextElement();

        /* if we didn't hit it give a warning */
        if (prod.num_reductions() == 0)
          {
            /* count it *
            emit.not_reduced++;

            /* give a warning if they haven't been turned off */
            if (!emit.nowarn)
            {
              System.err.println("*** Production \"" + 
                          prod.to_simple_string() + "\" never reduced");
              lexer.warning_count++;
            }
          }
      }
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*

  /** Convert to a string. */
  public String toString()
    {
      String result;
      int cnt;

      result = "-------- ACTION_TABLE --------\n";
      for (int row = 0; row < num_states(); row++)
      {
        result += "From state #" + row + "\n";
        cnt = 0;
        for (int col = 0; col < under_state[row].size(); col++)
          {
            /* if the action is not an error print it */ 
            if (under_state[row].under_term[col].kind() != parse_action.ERROR)
            {
              result += " [term " + col + ":" + under_state[row].under_term[col] + "]";

              /* end the line after the 2nd one */
              cnt++;
              if (cnt == 2)
                {
                  result += "\n";
                  cnt = 0;
                }
            }
          }
          /* finish the line if we haven't just done that */
        if (cnt != 0) result += "\n";
      }
      result += "------------------------------";

      return result;
    }

  /*-----------------------------------------------------------*/

}


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