proposition: Lemma minus_a_a : forall a, a - a = zero.
proof: Proof. induction a; simpl. - easy. - destruct a1. * destruct le_lt_dec; [easy | lia]. * now rewrite compare_refl, Nat.compare_refl. 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)