Homotopy Type Theory limit of a net > history (Rev #2)

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Definition

In premetric spaces

Let TT be a directed type, and let SS be a TT-premetric space. Given a directed type II, a limit of a net x:ISx: I \to S is a term l:Sl:S with

λ: ϵ:T N:I i:I(iN)(x i ϵl)\lambda: \prod_{\epsilon:T} \Vert \sum_{N:I} \prod_{i:I} (i \geq N) \to (x_i \sim_{\epsilon} l) \Vert

Of Cauchy approximations

Let RR be a Archimedean ordered integral domain with a dense strict order, and let R +R_{+} be the semiring? of positive terms in RR. If both TT and II are R +R_{+}, then a limit of a Cauchy approximation x:R +Sx: R_{+} \to S is a term l:Sl:S with

x:R +Sc(x): δ:R + η:R +x δ δ+ηlx:R_{+} \to S \vdash c(x):\prod_{\delta:R_{+}} \prod_{\eta:R_{+}} x_\delta \sim_{\delta + \eta} l

In convergence spaces

Sequences

A limit of a sequence is a limit of a net that happens to be a sequence.

See also

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