proposition: Lemma set_meet1 x : set_meet [set x] = x.
proof: Proof. by apply/le_anti; rewrite set_meet_lb // set_meet_ge_lb ?lb_set1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype choice order) mathcomp(ssrnat bigop classical_sets)