proposition: Lemma rregP x : reflect (rreg x) (x != 0).
proof: Proof. by apply: (iffP idP) => [/mulIf | /rreg_neq0]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)