proposition: Lemma signr_inj : injective (fun b : bool => (-1) ^+ b : R).
proof: Proof. exact: can_inj (fun x => 0 >= x) signr_le0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)