proposition: Lemma cpoint_ball x r : 0 < r -> cpoint (ball x r) = x.
proof: Proof. move=> r0; rewrite /cpoint; case: xgetP => [y _ [s] /(ball_inj r0)[]//|]. by move=> /(_ x)/forallNP/(_ r). Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrint ssrnum finmap matrix) mathcomp(rat interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality set_interval Rstruct) ereal reals signed topology prodnormedzmodule