proposition: Lemma nf_inv2 : forall a n b, nf (cons a n b) -> nf b.
proof: Proof. unfold nf; cbn; destruct a, b; auto with T1. destruct (nf_b (cons b1 n0 b2)); auto. destruct (nf_b (cons b1 n1 b2)); auto. destruct (nf_b (cons a1 n a2)); auto. 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)