cooltt VS pony-tutorial

If you're looking for stuff pushing the boundaries of PL research, Agda (especially Cubical Agda) might be cool to look at. It's got lots of cutting edge stuff in it, pushing the boundaries of what is currently possible with dependent type theory. It's not the only language out there with cubical features (see also: cooltt), but it's probably one of the more fleshed-out implementations in terms of being practically useful. The 1Lab makes heavy use of it. There's also Introduction to Univalent Foundations of Mathematics with Agda that might be interesting to look at too!

I don't think that there is a book written about Pony, but the tutorial and the list of patterns (WIP) are all you need to learn the language.

[Pony](https://tutorial.ponylang.io/): actors, reference capabilities, object capabilities.

Pony is a relatively young but interesting language with capabilities-security.

Well, depends on how you define ownership. Pony 's type system has reference capabilities which let you define who's allowed to do what to a reference and part of it sort of deals with ownership (along the lines of "this actor is allowed to do Y to the reference, other actors are allowed to do Z"). You can eg. have methods that return an isolated value that guarantees that there are no other references to that value, meaning it's automatically thread safe. You can also define things as vals which says that they are globally immutable, refs which give the current actor read/write capabilities but can't be shared with other actors

The alternatives are:

- Division must be impure (because it can throw an exception)

- Division must be partial - i.e. return Option[Int].

Both seem worse compared to defining division by zero as zero. Coq, Lean, and Pony do the same. https://github.com/ponylang/pony-tutorial/blob/master/conten...