proposition: Lemma natr_norm_int x : x \is a int_num -> `|x| \is a nat_num.
proof: Proof. by move=> /intrP[m ->]; rewrite -intr_norm rpred_nat_num ?natr_nat. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)