proposition: Lemma predn_int (n : nat) : (0 < n)%N -> n.-1%:Z = n%:Z - 1.
proof: Proof. exact: intZmod.predn_int. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)