proposition: Lemma intrV (n : int) : n \in [:: 0; 1; -1] -> n%:~R ^-1 = n%:~R :> R.
proof: Proof. by case: (intP n)=> // [|[]|[]] //; rewrite ?rmorphN ?invrN (invr0, invr1). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)