Getting rid of instance-of?

[rossberg]

With the recent move towards focussing on more coarse-grained actors, do we still need instance-of?

Getting rid of instance-of would simplify various other things:

• Class declarations would be pure, avoiding library issues.
• We wouldn't need Class types.
• We wouldn't need to distinguish class functions.
• We wouldn't need like types.
• Classes could be structurally typed, avoiding more interop issues.
• Objects wouldn't need to carry magic class fields.
• We wouldn't need to distinguish shared from non-shared object types (I think).

Overall, we are buying into a lot of complexity just to support instance-of.

[nomeata]

@paulyoung, with the “user” perspective, do you have an opinion here?

[ninegua]

Please help me understand the proposal here, was it to drop supporting instance-of from the actorscript language or dropping instance-of from system interface?

If latter, do we have other proposals to implement distributed payment?

[nomeata]

Just from ActorScript

[paulyoung]

@nomeata my only concern is that we seem to be planning on using “instance of” checks to get some guarantees based on “only my actor can create instances of this class”. I’d need to look up a concrete example.

I haven’t used the x is X syntax for anything (yet) and would happily use some other prescribed mechanism to achieve the above.

[paulyoung]

People more familiar with OOP might find it strange but I think it’s fine to say “This is/isn’t how you do things in ActorScript”

It might have some utility in emulating sum types in the short term but I wouldn’t make that a factor in this decision.

It sounds like this will simplify the language which seems better for everyone.

[paulyoung]

@rossberg, are you proposing that the class syntax (that defines both a term and type of the same name) stay the same?

I do think there’s some convenience in having the type defined on my behalf as opposed to having to define the type manually when using a function that returns a record.

[rossberg]

@ninegua, @paulyoung, yes, that drops that ability from the language only (a similar question could be raised for the API, but that's a different discussion). The reason for considering this being that it looks like supporting fine-grained actor-based control patterns like that is no longer a priority for v1. In particular, I got that we most likely don't want to do payment that way.

@paulyoung, yes, the class syntax would stay the same. But it would become almost entirely syntactic sugar for a function definition plus a type definition.

[rossberg]

@paulyoung, in a way this actually provides a the more puristic version of OO -- instance-of has always been counter to that.

I don't think sum type should be implemented with instance-of. We should simply add them properly, but that's not a high priority right now.

[paulyoung]

This all sounds good to me 👍