proposition: Lemma unitf_gt0 x : 0 < x -> x \is a GRing.unit.
proof: Proof. by move=> hx; rewrite unitfE eq_sym lt_eqF. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)