proposition: Lemma lregN x : lreg x -> lreg (- x).
proof: Proof. by move=> reg_x y z; rewrite !mulNr => /oppr_inj/reg_x. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)