[tel]

I'm not a big fan of languages allowing mutability anywhere. You can use it, sure, but advertise in big bold letters as to where. This plays out repeatedly for any side effect.

There are some OO systems with effect types I suppose. Those would be interesting.

There are also OO systems that don't have mutability. But I think that it you remove mutation, all that class nonsense, and are careful with subtyping (since it breaks things badly often) then you basically have (badly typed) ML modules with open recursion.

The open recursion (a.k.a. late binding) bit is probably the most interesting thing but you can play with it in Typed LC just fine. It's just another form of recursion.

[klibertp]

> There are some OO systems with effect types I suppose. Those would be interesting.

Nim has something IIRC, but I didn't look into it yet.