proposition: Lemma contractK : cancel (@contract R) (@expand R).
proof: Proof. apply: (onS_can [pred r | `|r| <= 1]%R (@contract_le1 R)). exact: inj_can_sym_on (@expandK R) (on2W (@contract_inj R)). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(fsbigop cardinality set_interval) reals signed topology constructive_ereal