proposition: Lemma edist_sym (x y : X) : edist (x, y) = edist (y, x).
proof: Proof. by rewrite /edist /=; under eq_fun do rewrite ball_symE. 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