proposition: Lemma joinKUC y x : x `|` (y `|` x) = x `|` y.
proof: Proof. exact: (@meetKIC _ L^d). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)