Section BDDand_results.
Variable cfg : BDDconfig.
Variable ul : list ad.
Variable node1 node2 : ad.
Hypothesis cfg_OK : BDDconfig_OK cfg.
Hypothesis ul_OK : used_list_OK cfg ul.
Hypothesis used1 : used_node' cfg ul node1.
Hypothesis used2 : used_node' cfg ul node2.
Definition BDDand :=
match BDDneg cfg ul node1 with
| (cfg1, node1') =>
match BDDneg cfg1 (node1' :: ul) node2 with
| (cfg2, node2') =>
match BDDor cfg2 (node2' :: node1' :: ul) node1' node2' with
| (cfg3, node3) => BDDneg cfg3 (node3 :: ul) node3
end
end
end.

Lemma BDDand_var_le :
Nleb (node_height (fst BDDand) (snd BDDand))
(BDDvar_max (node_height cfg node1) (node_height cfg node2)) = true.