atom improvements

[mpenet]

Just for the record, a few things that are "missing":

• watches
• validation
• compare-and-set!
• metadata support

[mpenet]

watches and validation are part of an inherited abstract class in clojure/java, it's shared by other ref types, we might want to do the same (or not). But I don't know what's the long term goal here, it depends if there is a plan to add other ref types (agents, refs) or not (as they are not so popular in clojure, at least in public projects).

[thomasmulvaney]

It might be possible to get away with doing this in pixie itself rather than in rpython. In fact atoms are used in only 2 or 3 places from what I can tell in the underlying rpython code (basically where one might use ^:dynamic) in clojure. Maybe we could redefine it in pixie using deftype and give it all the other bells and whistles quite easily with protocols like IWatch

[mpenet]

Yes, it's a possibility, my (very uneducated) guess is that atoms are done with rpython for performance reasons, seems like they would be more lightweight this way as well, at least until jit kicks in. And since they are used in some important code such as some stateful transducers, it makes sense. But I might be wrong, I don't know well enough about pixie internals tbh.
Probably something for @halgari to look into.

[mpenet]

btw metadata support is in #425

[egregius313]

Is this still of interest? I would be happy to experiment with adding the other features.

[thomasmulvaney]

Your welcome to add anything that tickles your interests. These atom improvements would certainly be great!