samsara VS jank

> IME it's the other way around, per-object individual lifetimes is a rare special case

It depends on your application domain. But in most cases where objects have "individual lifetimes" you can still use reference counting, which has lower latency and memory overhead than tracing GC and interacts well with manual memory management. Tracing GC can then be "plugged in" for very specific cases, preferably using a high performance concurrent implementation much like https://github.com/chc4/samsara (for Rust) or https://github.com/pebal/sgcl (for C++).

> Just for example: "it needs a GC" could be the heart of such an argument

Rust can actually support high-performance concurrent GC, see https://github.com/chc4/samsara for an experimental implementation. But unlike other languages it gives you the option of not using it.

The compiler support you need is quite limited. Here's an implementation of cycle collection in Rust: https://github.com/chc4/samsara It's made possible because Rust can tell apart read-only and read-write references (except for interior mutable objects, but these are known to the compiler and references to them can be treated as read-write). This avoids a global stop-the-world for the entire program.

Cascading deletes are rare in practice, and if anything they are inherent to deterministic deletion, which is often a desirable property. When they're possible, one can often use arena allocation to avoid the issue altogether, since arenas are managed as a single object.

There are concurrent GC implementations for Rust, e.g. Samsara https://redvice.org/2023/samsara-garbage-collector/ https://github.com/chc4/samsara that avoid blocking, except to a minimal extent in rare cases of contention. That fits pretty well with the pattern of "doing a bit of GC every frame".

There are a number of efforts along these lines, the most interesting is probably Samsara https://github.com/chc4/samsara https://redvice.org/2023/samsara-garbage-collector/ which implements a concurrent, thread-safe GC with no global "stop the world" phase.

Nice blog post! I also wrote a concurrent reference counted cycle collector in Rust (https://github.com/chc4/samsara) though never published it to crates.io. It's neat to see the different choices that people made implementing similar goals, and dumpster works pretty differently from how I did it. I hit the same problems wrt concurrent mutation of the graph when trying to count in-degree of nodes, or adding references during a collection - I didn't even think of doing generational references and just have a RwLock...

There's an effort afoot to bring this to the Clojure world, with the lovely name jank: https://jank-lang.org

I also liked that reference since I had not heard of Jank before. It is a work in progress so I just added a calendar entry for 9 months from now to check it out. https://jank-lang.org/

There will be a lot of room for this, once I build out more of the features. In particular, there will be a lot of Clojure libraries which need to gain jank support. Clojure doesn't require "porting", so to speak, since it has a special .cljc file which can use reader conditionals to check the host that it's in (clj, cljs, cljr, jank, etc). So anywhere those libs are using Java interop, we'd need to wrap it to use native interop instead.

On the compiler and tooling itself, I have some open issues here: https://github.com/jank-lang/jank/issues

The vast majority of it is heavy C++ work, though. Outside of that, the biggest gains will come from time spent on packaging, distribution, and testing on various platforms.

And if none of that sounds interesting or applicable, don't worry. Just be sure to join the Slack channel and hang out with us. :)

On the top of using C++ for scripting, and related to the discussion of CERN's ROOT/Cling, I am developing a Clojure dialect on C++/LLVM called jank: https://jank-lang.org/

jank is a true Clojure, meaning you get interactive, REPL-based development and a whole stdlib of persistent, immutable data structures and functions to transform them. But it's also C++, so you can write inline C++ within your jank source, and interpolate jank values within that. You can link with existing native code using LLVM and you can embed jank into your existing native projects to use for scripting.

jank is pre-alpha, right now, and I've only been showing it to Clojure devs so far, but there's a huge audience of C++ devs which may be interested in introducing Clojure to their native code.

jank (https://jank-lang.org/) is a Clojure dialect on LLVM with C++ interop. In this talk, Jeaye will cover jank's use cases, some challenges around building a native Clojure dialect, and some insights about Clojure itself found only by spelunking deep into the Clojure compiler.

I wonder if Jank [1] could be such a Lisp? I haven't played around with it, but I really like the idea and would love to see it get more traction.

[1]: https://jank-lang.org/

This isn't usable yet, but in active development by the author, and looks promising: https://jank-lang.org/

Jank looks pretty legit: https://jank-lang.org/