proposition: Lemma succ_is_add_one a: T1succ a = a + one.
proof: Proof. by elim:a => // a _ n b Hb /=; rewrite T1ltn0 addn0 Hb; case a. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)