proposition: Lemma enum_grect_uniq r : uniq (enum_grect r).
proof: Proof. case: r => x0 x1 y0 y1; rewrite allpairs_uniq ?zspan_uniq //. by apply: in2W => -[_ _] [x y] [-> ->]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(div choice order ssralg ssrnum ssrint intdiv) fourcolor(hypermap)