proposition: Lemma gr_proper_refine s r : gr_proper (iter s refine_rect r) = gr_proper r.
proof: Proof. by elim: s => // s; rewrite /gr_proper garea_refine_rect !double_gt0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)