reserve a,b,i,j,k,l,m,n for Nat;

theorem
  for f,g be complex-valued FinSequence holds len (f - g) = min (len f, len g)
  proof
    let f,g be complex-valued FinSequence;
    reconsider h = -g as FinSequence of COMPLEX by NEWTON02:103;
    h = (-1)(#)g by VALUED_1:def 6; then
    dom h = dom g by VALUED_1:def 5; then
    A1: len h = len g by FINSEQ_3:29;
    f-g = f+h by VALUED_1:def 9;
    hence thesis by FLS,A1;
  end;
