proposition: Lemma near_in_itv {R : realFieldType} (a b : R) : {in `]a, b[, forall y, \forall z \near y, z \in `]a, b[}.
proof: Proof. exact: interval_open. 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