reserve n for non zero Nat,
  j,k,l,m for Nat,
  g,h,i for Integer;

theorem
  for n be non zero Nat for F be Tuple of n,BOOLEAN st F = 0*n holds
  Intval F = 0
proof
  let n be non zero Nat;
  let F be Tuple of n,BOOLEAN such that
A1: F = 0*n;
A2: 1 <= n by NAT_1:14;
  n <= len F by CARD_1:def 7;
  then F/.n = F.n by A2,FINSEQ_4:15
    .= FALSE by A1;
  then Intval F = Absval F by BINARI_2:def 3;
  hence thesis by A1,BINARI_3:6;
end;
