proposition: Lemma join_idPr {x y} : reflect (x `|` y = y) (x <= y).
proof: Proof. exact: (@meet_idPr _ 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)