proposition: Lemma natrP x : reflect (exists n, x = n%:R) (x \is a nat_num).
proof: Proof. apply: (iffP idP) => [|[n ->]]; rewrite // natrE => /eqP <-. by exists (Def.trunc x). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)