proposition: Lemma ge_leif x y C : x <= y ?= iff C -> (y <= x) = C.
proof: Proof. by case=> le_xy; rewrite eq_le le_xy. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)