proposition: Lemma contract_le1 x : (`|contract x| <= 1)%R.
proof: Proof. by case: x => [r| |] /=; rewrite ?normrN1 ?normr1 // (ltW (contract_lt1 _)). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed