proposition: Lemma mule_def_neq0_infty x y : x != 0 -> y \isn't a fin_num -> x *? y.
proof: Proof. by move: x y => [x| |] [y| |]// x0 _; rewrite /mule_def (negbTE x0). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed