reserve n,m for Nat;
reserve p,q,r for Element of Nat_Lattice;
reserve p,q,r for Element of Nat_Lattice;

theorem Th6:
  hcflat.(q,p)=hcflat.(p,q)
proof
  thus hcflat.(q,p)=p"/\"q by LATTICES:def 2
    .=hcflat.(p,q);
end;
