proposition: Lemma mulz_Nsign_abs m : ((-1) ^+ (0 < m)%R * `|m|%:Z)%R = - m.
proof: Proof. by rewrite abszE mulr_Nsign_norm. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)