proposition: Lemma size_deriv p : size (deriv p) = (size p).-1.
proof: Proof. rewrite /deriv /deriv_loop. case: p => [|a p] //=. elim: p 1 => [|b p IHp] n //=. by rewrite IHp. Qed.
imports: Coq(ZArith Reals) Coquelicot(Coquelicot) mathcomp.ssreflect(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype bigop) Flocq(Core) Stdlib MathComp Interval Xreal Basic_rec