proposition: Lemma itv_leEmeet i1 i2 : (i1 <= i2) = (itv_meet i1 i2 == i1).
proof: Proof. by case: i1 i2 => [? ?] [? ?]; rewrite /eq_op/=/eq_op/= eq_meetl eq_joinl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)