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＜追加参考＞
圏論の極限と位相の極限の関係（下記）
（これ読むと、ε-δはもう古いというのが、よく分かるね（＾＾　
　ε-δの一般化が、ε近傍系（可算）で、さらに一般化が”filter”（可算に限らない）で、さらなる一般化が”Limit (category theory)”ですね
　”filter”が分からないと、下記の”Example”が分からんわけですね（＾＾； ）

https://en.wikipedia.org/wiki/Limit_(category_theory)
Limit (category theory)

Examples
Topological limits.
Limits of functions are a special case of limits of filters, which are related to categorical limits as follows.
Given a topological space X, denote by F the set of filters on X, x ∈ X a point, V(x) ∈ F the neighborhood filter of x, A ∈ F a particular filter and F_{x,A}={G∈ F｜ V(x)∪A ⊂ G}the set of filters finer than A and that converge to x.
The filters F are given a small and thin category structure by adding an arrow A → B if and only if A ⊆ B.
The injection I_{x,A}:F_{x,A}→ F becomes a functor and the following equivalence holds :
x is a topological limit of A if and only if A is a categorical limit of I_{x,A}
(引用終り)
以上