Type erasure and forgetful functors

24 Oct 2019 ⇐ Notes archive

(This is an entry in my technical notebook. There will likely be typos, mistakes, or wider logical leaps — the intent here is to “let others look over my shoulder while I figure things out.”)

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Type erasure and forgetful functors, at least in terms of intuition, feel very similar.

One removes detail (e.g. Publishers.Zip -> AnyPublisher) and the other strips structure, leaving the underlying set behind (a monoid or group being mapped onto its base set).

Wonder if there’s a way to visualize this by considering eraseToAnyPublisher as a sort of forgetful endofunctor into a subcategory of Swift (hand waving) that only contains AnyPublishers?