proposition: Lemma eqe_oppLR x y : (- x == y) = (x == - y).
proof: Proof. by move: x y => [r0| |] [r1| |] //=; rewrite !eqe eqr_oppLR. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed