proposition: Lemma signrN b : (-1) ^+ (~~ b) = - (-1) ^+ b :> R.
proof: Proof. by case: b; rewrite ?opprK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)