proposition: Lemma single_nf : forall a n, nf a -> nf (cons a n zero).
proof: Proof. unfold nf; now cbn. Qed.
imports: Coq(Arith Max Bool Lia Compare_dec Relations Ensembles Wellfounded Bool RelationClasses Operators_Properties ArithRing Logic.Eqdep_dec) hydras(More_Arith Restriction DecPreOrder) hydras(OrdNotations)