function out = subsref (f, x)
  switch x.type
    case "()"
      n = f.polynomial;
      out = filter (n.poly, 1, x.subs{1});
    case "."
      fld = x.subs;
      if (strcmp (fld, "polynomial"))
        out = f.polynomial;
      else
        error ("@FIRfilter/subsref: invalid property \"%s\"", fld);
      endif
    otherwise
      error ("@FIRfilter/subsref: invalid subscript type for FIR filter");
  endswitch
endfunction