public PGValue visit(NodeListOptional n, Node argu) {
   ParamList_pg pl = new ParamList_pg();
   if (n.present()) {
     PGValue _ret = null;
     int _count = 0;
     for (Enumeration<Node> e = n.elements(); e.hasMoreElements(); ) {
       PGValue p = (PGValue) e.nextElement().accept(this, argu);
       if (p != null) pl.Insert(p);
       _count++;
     }
     return pl;
   } else return null;
 }
 /** f0 -> "MAIN" f1 -> StmtList() f2 -> "END" f3 -> ( Procedure() )* f4 -> <EOF> */
 public PGValue visit(Goal n, Node argu) {
   PGValue _ret = null;
   ParamList_pg pl;
   n.f0.accept(this, argu);
   if (met_name.equals("MAIN")) {
     // System.out.println("MAIN");
     n.f1.accept(this, n.f1);
     return null;
   }
   n.f2.accept(this, argu);
   pl = (ParamList_pg) n.f3.accept(this, argu);
   n.f4.accept(this, argu);
   return pl.GetFirst();
 }
  /** f0 -> "CALL" f1 -> Exp() f2 -> "(" f3 -> ( Exp() )* f4 -> ")" */
  public PGValue visit(Call n, Node argu) {

    // NOTE: bug fix by jurgens@cs 10/30/07, kgo@cs 11/14/07
    //
    // details: local_arg_size was previously initialized to 20.
    // This resulted in TEMP values being overwritten by the caller.
    // For recursive calls, the overwritten values were bugs if any
    // thing stored in an overwritten temp was used after the
    // recursive call.  For this reason, we now make a copy of the
    // entire temp space before each call.

    n.f0.accept(this, argu);

    PGValue function_addr = n.f1.accept(this, argu);

    if (!(function_addr instanceof Label_pg)) {
      System.err.println("error in CALL");
      System.exit(0);
      return null; // Will never actually be reached.
    }

    String m_name = function_addr.GetLabel();

    n.f2.accept(this, argu);

    // Caller saves all local variables.
    PGValue[] saved_locals = new PGValue[TPV.length];
    System.arraycopy(TPV, 0, saved_locals, 0, TPV.length);

    // Copy call args into first N temps.
    ParamList_pg pl = (ParamList_pg) n.f3.accept(this, argu);

    // NOTE: we save and return the TEMPs for the caller, so we are
    // free to update the TPV array at this point.  kgo@cs fixed a
    // bug where this statement caused the callee to have TPV
    // side-effects for the caller.

    // NOTE: that if the method had no parameters, pl will be null.
    // This bug was discovered by Prof. Todd Millstein todd@cs.

    // check to see if the callee has any arguments and if so, pass
    // them into the TPV temp array using the caller's parameters
    if (pl != null) {
      int num_params = pl.GetVal();
      PGValue[] param_list = pl.GetList();

      for (int i = 0; i < num_params; i++) {
        TPV[i] = param_list[i];
      }
    }

    n.f4.accept(this, argu);
    met_name = m_name;
    boolean old_start = start;
    boolean old_stop = stop;
    start = true;
    stop = false;
    // System.out.println("No NO NO 222" + met_name);
    PGValue _ret = pg_root.accept(this, pg_root);
    // System.out.println("No NO NO");
    start = old_start;
    stop = old_stop;

    // Restore saved local variables.
    TPV = saved_locals;

    return _ret;
  }