proposition: Lemma subeK x y : y \is a fin_num -> x - y + y = x.
proof: Proof. by move: x y => [x| |] [y| |] //; rewrite -EFinD subrK. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed