proposition: Lemma eqr_norm2 x y : (`|x| == `|y|) = (x == y) || (x == -y).
proof: Proof. exact: real_eqr_norm2. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)