Programming with OCaml's Local Mode | OCaml Unboxed

[@huge_letters]

thanks for the series :) still hard to wrap my head around most of the concepts, probably will once I get to actually use this but was very interesting to watch

[@12332a]

Heyy can u plzz tell me that a B.E Cse graduate can apply in jane street or not..

[@bjzaba]

Great series, thank you, this feature is very exciting! It would be nice to get some clarification on what modes are compared to modalities (this came up in passing when talking about the global field). I was thinking this whole video series that "modes" were a Jane Street-ism for "modality". I had felt it was a little bit unfortunate, as there is already a notion of "mode" in logic programming which is in relation to how the parameters of a predicate can be instantiated. If you're familiar with bidirectional typing, this is the same as how you can mark parts of the typing judgements as inputs or outputs - I even think some authors refer to these as modes as well.

[@RichardEisenberg-JS]

Yes, there are lots of different uses of the terminology out there. I don't particularly defend our choices, but instead I acknowledge that I think any choice of term would have thrown off some potential learners. As for modality vs mode: We use modality to mean a function from mode to mode. Suppose we have a record r at mode m whose type has a field x with a modality f. Then an access of r.x is at mode f(m). The `global` modality is the constant function that always returns `global`. But we have imagined other modalities that actually depend on their argument.

[@bjzaba]

@@RichardEisenberg-JS Cool, thanks for the explanation! Yeah figuring out terminology for new things is definitely hard, and I don’t envy the compromises you have to make. There's always going to be people confused or frustrated and it's hard to predict that in the future - it could be fine, or it could be grumbled about for years, and there's only so many words to choose. Anyway, thanks again for your work and your efforts in explaining this stuff, it's greatly appreciated!

[@moazzammoriani1656]

Thank you for this series! I'm curious about the speedup and performance gains that modal types offer. Are there any benchmarks currently available?

[@RichardEisenberg-JS]

I don't have benchmarks to report. Part of the problem with benchmarks is that it's hard to make any that are not misleading. That is, I bet I could get an arbitrary percentage speedup by switching to locals, if I have the freedom to write my own program, so writing my own program is not a good way to address this. I could use existing programs, but because using locals well requires some annotations, those programs would have to be edited. How much should we edit? Now that locals exist, we might be able to make large restructuring to a program that will make it clearer without losing performance.... but how does the benchmark take that into account? I'm not trying to say that these problems don't have solutions, just that "measure the perf improvement" is never quite as easy as it sounds. Incidentally, the biggest place within Jane Street that makes use of locals isn't around performance improvement, but is instead around code improvement. That is, there are some applications with performance requirements. Previous to locals, those applications used other techniques to meet their needs. Now with locals, programs can be written more idiomatically (making them easier to maintain), all without losing performance. So the biggest win -- maintainability -- is even harder to measure.

[@ps-eo3rr]

Hey give me an interview I'm pretty good. Software developer. Thought I'd ask. Why not, you know