proposition: Lemma sgrEz x : sgr x = (sgz x)%:~R.
proof: Proof. by rewrite !(fun_if intr). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)