theorem Th69:
  latt F = latt (L,F)
proof
  ex o1, o2 being BinOp of F st o1 = join(L)||F & o2 = met(L)||F & latt (L
  ,F) = LattStr (#F, o1, o2#) by Def14;
  hence thesis by FILTER_0:def 9;
end;
