proposition: Lemma mule_def_infty_neq0 x y : x \isn't a fin_num -> y!= 0 -> x *? y.
proof: Proof. by move: x y => [x| |] [y| |]// _ y0; rewrite /mule_def (negbTE y0). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed