reserve a, b, k, n, m for Nat,
  i for Integer,
  r for Real,
  p for Rational,
  c for Complex,
  x for object,
  f for Function;

theorem
  (for n holds scf(r).n <> 0) implies r is irrational
proof
  assume
A1: for n holds scf(r).n <> 0;
  not ex n st for m st m >= n holds scf(r).m = 0
  proof
    let n;
    take n;
    thus thesis by A1;
  end;
  hence thesis by Th42;
end;
