
theorem Th2:
  for L being non empty addLoopStr, F being FinSequence of (the
  carrier of L)* holds dom Sum F = dom F
proof
  let L be non empty addLoopStr, F be FinSequence of (the carrier of L)*;
  len Sum F = len F by MATRLIN:def 6;
  hence thesis by FINSEQ_3:29;
end;
