theorem
  for s being SCM+FSA-State, t being Element of SCM+FSA-Data-Loc, u
  being Integer holds SCM+FSA-Chg(s,t,u).NAT = s.NAT
proof
  let s be SCM+FSA-State, t be Element of SCM+FSA-Data-Loc, u be Integer;
  (SCM*-VAL*SCM+FSA-OK).t = INT & {t} = dom(t .--> u) by Th5;
  then not NAT in dom(t .--> u) by Th4,NUMBERS:7,TARSKI:def 1;
  hence thesis by FUNCT_4:11;
end;
