theorem Th28:
  for f being len-total to-naturals homogeneous NAT*-defined Function holds
  f is quasi_total Element of HFuncs NAT
proof
  let f be len-total to-naturals homogeneous NAT*-defined Function;
  reconsider f9=f as Element of HFuncs NAT by Th27;
  f9 is quasi_total
  by Def2;
  hence thesis;
end;
