Paper: Recovering Purity with Comonads and Capabilities

[glaebhoerl]

I thought you might find this interesting:

http://semantic-domain.blogspot.com/2019/07/all-comonads-all-time.html
https://www.cl.cam.ac.uk/~nk480/popl20-cap-submission.pdf

There are some similarities with Rust's (planned) const-generics system (swapping const for Pure as appropriate):

• const expressions can only refer to const variables

• const values can lose their constness and be used as normal runtime/impure values (the comonadic "extract", I don't remember which Greek letter they used for it in the paper)

• A const fn can be applied to a const expression to yield a const result; a non-const fn can't

And some differences:

• const T in Rust isn't a type, but part of the "generics" system

• Relatedly, there's no comonadic "duplicate" (const T -> const (const T))) -- which might make more sense if const were a type

• And of course, one of them is for tracking "known at compile-time" and the other is for tracking purity.