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Stream: learning: reading & references

Topic: Cartesian Closed Containers


view this post on Zulip Ian Price (Aug 07 2026 at 13:17):

In Altenkirch, Levy & Staton's "Higher Order Containers" they give a proof that the category of containers over Set (aka Poly) is cartesian closed. I would like to know if there are proofs that Cont(C) is cartesian closed for other C, e.g., when C is complete. (Specifically I'm interested in categories of assemblies/modest sets)

It's possible that their proof generalises easily, and my lack of familiarity with ends prevents me from seeing that.

view this post on Zulip Tom de Jong (Aug 07 2026 at 13:48):

Reading the start of Section 2, I believe all mentions of Set are really mentions to some type-theoretic universe, so I would expect most of the paper (for instance, without the alternative proof sketched right before Section 5) to apply to any category C that is a model of extensional MLTT with the type formers described at the start of Section 2. (The requirement on the booleans being disjoint actually follows from having the type of booleans in the universe.) In particular, it should work for the category of assemblies.
(Link to a publicly available copy of the paper)

view this post on Zulip Ian Price (Aug 07 2026 at 14:17):

thanks tom

view this post on Zulip Evan Cavallo (Aug 07 2026 at 18:45):

Another presentation of this result in some generality is Theorem 4.4 In Von Glehn's thesis https://doi.org/10.17863/CAM.16245. (You'll have to chase down the ambient hypotheses...)

view this post on Zulip Ian Price (Aug 09 2026 at 09:45):

Thanks Evan, this was a reference I should have checked by somehow slipped my mind