fact: Definition intrE x : (x \is a int_num) = (x \is a nat_num) || (- x \is a nat_num) := @ssrnum.Num.Theory.mc_2_0.intrE R x.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)