proposition: Lemma itvxxP y x : reflect (y = x) (y \in `[x, x]).
proof: Proof. by rewrite itvxx; apply/eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)