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TauCeti.Computability.Enumeration.Converges

Convergence of finite-stage enumerations #

Under monotone stages, the finite stages A s of an enumeration approximate its limit in the sense of limit approximations: any function restricted to the stages converges pointwise to the same function restricted to the limit. In particular the set-oracle answers of the stages converge to those of the limit set (TauCeti.Oracle.Single.Code.converges_setAnswers_stageLimit).

Main results #

theorem TauCeti.Enumeration.converges_indicator_stageLimit {M : Type u_1} [Zero M] {A : ℕ → Finset ℕ} (hA : Monotone A) (f : ℕ → M) :
Approximation.Converges (fun (s : ℕ) => (↑(A s)).indicator f) ((stageLimit A).indicator f)

Under monotone stages, the indicator functions of the stages converge to the indicator function of the limit. This is Mathlib's Monotone.indicator_eventuallyEq_iUnion for the stages.