Until last year, we used to teach continuations to our students, relying on a simple usage of Oleg Kiselyov’s delimcc library (nothing fancy, just as an introduction). Now that OCaml 5 is here, I was wondering whether someone had developed a PPX or library hiding a bit of the Effect module machinery…

I believe @avsm has a WIP branch that adds syntax for effect handlers in OCaml 5 with the aim to make it easy for teaching them.

I do indeed have the same problem as @grayswandyr , in that I’m planning on teaching effects/concurrency in my undergraduate courses at Cambridge from next year. I don’t think PPX is satisfactory for teaching due to the cognitive overhead of the syntax. I’ve got a WIP rebase of the effects syntax b…

I’ve revived some old code that implements delimited control operators (shift/reset, control/prompt) over effect handlers and pushed it as a separate library. [image] GitHub - kayceesrk/delimcc_of_fxhandler: Delimcc primitives from OCaml 5... Delimcc primitives from OCaml 5 effect handl…

That’s great. I’m going to test it right away, thanks.

I also teach continuations to my students :slight_smile: I seem to recall that effects are not sufficient as a drop-in replacement for delimcc because the continuations in effects are one-shot. That wouldn’t work for some of my examples.

Delimited continuations exposed by effect handlers on OCaml 5 are indeed one-shot. However, GitHub - kayceesrk/delimcc_of_fxhandler: Delimcc primitives from OCaml 5 effect handlers provides multishot continuations by building on top of GitHub - dhil/ocaml-multicont: multi-shot continuations in OCaml .…

Right, I was thinking of this thread . So I guess as long as you are careful about resources you can do it.

Not just resources. The fact that compiler optimisations break semantics is challenging to get around with careful programming. If you are careful with resources and avoid mutable state, then you will get the right semantics. This isn’t impossible but it is easy to get wrong.

Would you mind publishing the package on opam? It’d be easier to ask our sysadmin to install it on our lab machines like (s)he does with other opam packages. (If you can come up with a shorter name for our students to type the lib name, that’d be cool too :wink: )

Happy to. I shall get to it this week.

User-friendly continuations over OCaml 5 effects?

Ecosystem

kayceesrk June 23, 2023, 12:40am 12

The package is now on opam

Topic		Replies	Views
Radical new effect syntax for immediately resuming continuations Community ocaml	8	885	November 14, 2024
Effect composability: actual callstack vs syntactic scope Learning	2	297	November 27, 2025
Ppx lib for OCaml 5.0 Ecosystem compiler , ppx , dune	4	1032	March 23, 2022
OCaml 5 Effects syntax Learning effects	1	2995	July 20, 2022
Multi-shot continuations gone forever? Ecosystem	17	6418	December 14, 2022

User-friendly continuations over OCaml 5 effects?

Related topics