proposition: Lemma fromNat_addBn n m1 m2 : #m1 +# m2 = fromNat (n:=n) (m1 + m2).
proof: Proof. apply toNat_inj. rewrite toNat_addB !toNat_fromNat. by rewrite modnDm. Qed.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq fintype tuple zmodp div) ssrextra.tuple ssrextra.nat spec spec.properties operations mathcomp(ssralg)