koka VS wasm-effect-handlers

This post by the Koka-author is an update about what's currently being worked on: https://github.com/koka-lang/koka/discussions/339

Some programming language like JS, use path-based imports, that's not good for making a stabel API.

See https://api-extractor.com/pages/setup/configure_rollup/#:~:text=(The%20API%20Extractor,with%20that%20effort.)

And https://github.com/koka-lang/koka/issues/31#issuecomment-1482200826

It also offers a great Inversion of Control mechanism where everything is customisable, and, unlike Capability Objects, AESs also offer compatibility with type inference (you can pass functions doing IO to map, and it Just Works(TM)) and first-class control over stack frames (because really a continuation function is just some stack frames, which you can manually move to the heap if you want a closure; which means async is an effect!). It also is composable in ways Monads are not.

Koka and other languages implementing Algebraic Effect Systems make everything a user-defined case of coroutines: async is just another effect/Monadic type. Zig does something similar by having first class stack frames, making all function calls possibly asynchronous.

Super interesting, there is a proposal to add this to JavaScript and several languages that use this, unison, koka & eff. I had no idea this was even a thing!

Koka, already cited in this thread, early 2010s. Koka's first claim to fame was a usable effect system (at the type were, basically, effect systems were not usable in practice; in fact few languages have managed to do as well as Koka since). Now its author is working on cool implementation strategies for functional languages as well.

I'm a software engineer with 3 years of professional experience. I worked for 2 years at Microsoft on Azure Compute and now work at Google, working on improving Google search. I am the sole maintainer of the popular open-source library microlens with 80k downloads. I've also contributed to the Koka programming language developed at Microsoft Research.

By implementing all of those optimizations in the Koka programming language, they achieved GC overhead much less and execution time faster than the other languages including OCaml, Haskell, and even C++ in several algorithms and data structures that frequently keep common sub-structures of them, such as red-black trees. For more information, see the latest version of the paper.

This won't be a very deep answer, but to connect with the original post, programming in CPS is more closely related to delimited continuations than call/cc is because the continuations are just ordinary functions in the host language, unlike call/cc continuations which are a bit more complex.

As for why delimited continuations are not more popular, many people find shift/reset a bit difficult to program with. In particular the type systems for them are a bit odd and some variants like prompt/control don't have nice type systems for them. Currently, the closely related notion of (algebraic) effect handlers is quite popular in the functional language design community as something quite similar in expressive power but more intuitive for programming and with very natural typing. The Koka language has a lot of nice introductory resources if you are interested in learning more: https://github.com/koka-lang/koka . There's even a serious proposal for adding something based on these to webassembly: https://github.com/effect-handlers/wasm-effect-handlers .