proposition: Lemma eqr_norm_id x : (`|x| == x) = (0 <= x).
proof: Proof. by rewrite ger0_def. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)