proposition: Lemma eqNr x : (- x == x) = (x == 0).
proof: Proof. by rewrite eq_sym -addr_eq0 -mulr2n mulrn_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)