reason VS ocaml

Hey HN, at Ahrefs we have been working on an online book that hopefully helps React developers get up and running with Melange, an OCaml to JavaScript compiler. You can read more about Melange here: https://melange.re/.

There are still a few chapters that we'd like to add before considering it "complete", but it might be already helpful for some folks out there, that's why we decided to publish it early.

The book uses Reason syntax to implement React components using ReasonReact components. You can read more about both in:

https://reasonml.github.io/

ReScript is "Fast, Simple, Fully Typed JavaScript from the Future". What that means is that ReScript has a lightning fast compiler, an easy to learn JS like syntax, strong static types, with amazing features like pattern matching and variant types. Until 2020 it was called "BuckleScript" and is closely related to ReasonML.

This tracks with how I've seen "normal" languages converge on similar, flawed imitations of better type systems through tools and repurposed syntax. Thank you for confirming.

Do you have any recommendations or warnings regarding general languages which reach in the opposite direction? Reason[1] and F#[2] are both examples: they attach pre-existing ecosystems and compile-for-$PLATFORM tools to OCaml-like typing.

OCaml itself is also intriguing for personal projects. However, I'm worried the "GPL" in its standard library's LGPL license might scare people despite both the linking exception and Jane Street's MIT alternative.

1. https://reasonml.github.io/

ReasonML purely as a syntax layer on top of OCaml is still being updated and released[1]. Incidentally, I'm one of the maintainers of that project too :-)

With this Melange release, we're hoping to somewhat revive ReasonML and channel some folks back to the community from the perspective of a vertically integrated platform that has seen major investment in the past few years.

[1]: https://github.com/reasonml/reason

Quieted down, but I depend on projects with worst graphs:

https://github.com/reasonml/reason/graphs/contributors

ReasonML and ReScript are a (more or less the same) new syntax on top of OCaml. ReScript only targets JS, while ReasonML targets both JS and the native archs OCaml supports. Facebook and Bloomberg are using ReScript internally, afaik. Messenger.com is written in it. Facebook also maintains React bindings to ReScript.

https://rescript-lang.org/

https://reasonml.github.io/

There is also reasonml for Web development.

> OCaml’s configure script is also “normal”

If that’s this OCaml, it has a configure.ac file in the root directory, which looks suspicious for an Autotools-free package: https://github.com/ocaml/ocaml

You probably already know, but with OCaml 5 the only way to get flamegraphs working is to either:

* use framepointers [1]

* use LBR (but LBR has a limited depth, and may not work on on all CPUs, I'm assuming due to bugs in perf)

* implement some deep changes in how perf works to handle the 2 stacks in OCaml (I don't even know if this would be possible), or write/adapt some eBPF code to do it

OCaml 5 has a separate stack for OCaml code and C code, and although GDB can link them based on DWARF info, perf DWARF call-graphs cannot (https://github.com/ocaml/ocaml/issues/12563#issuecomment-193...)

If you need more evidence to keep it enabled in future releases, you can use OCaml 5 as an example (unfortunately there aren't many OCaml applications, so that may not carry too much weight on its own).

[1]: I haven't actually realised that Fedora39 has already enabled FP by default, nice! (I still do most of my day-to-day profiling on an ~CentOS 7 system with 'perf --call-graph dwarf', I was aware that there was a discussion to enable FP by default, but haven't noticed it has actually been done already)

11. OCaml - $91,026

> But .mli files do not help with the "no types in the source code" problém

It partially helps since it forces you to have types where they matters most: interfaces.

> And I did not experience any advantage of separate signature files so far,

100kLoc is already quite big! I'm starting to think I'm an outlier since a lot of people don't see the benefits :)

For me, it helps because I really don't want to see the implementation when I use an API. If I need to look at the implementation, it means the interface isn't well specified. All I need should be in the interface: types, docs, (abstract) types. And no more.

Typically, an .ml file will have more than what is exported, types won't be abstract but will have a concrete implementation, and type signatures may be missing. How would it feels like to use list if only https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml was available, instead of https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.mli?

Haskell tells you what is exported from a module, but it only shows you the names. To see the signatures, you need to rely on generated doc.

Arguably, since OCaml has includes, it suffers from the same problem, your ".mli" may have tons of include and it becomes harder to see what's exported without an external tool

> It partially helps since it forces you to have types where they matters most: exported functions

But the problém the OP has is not knowing the types when reading the source (in the .ml file).

> How would it feels like to use list if only https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml was available,

If the signature where in the source file (which you can do in OCaml too), there would be no problem - which is what all the other (for some definition of "other") languages except C and C++ (even Fortran) do.

No, really, I can't see a single advantage of separate .mli files at all. The real problém is that the documentation is often worse too, as the .mli is autogenerated and documented afterwards - and now changes made later in the sources need to be documented in the mli too, so anything that doesn't change the type often gets lost. The same happens in C and C++ with header files.

If you have been in the Ruby community for the past couple of years, it's possible that you're not a super fan of types or that this concept never passed through your mind, and that's totally cool. I myself love the dynamic and meta-programming nature of Ruby, and honestly, by the time of this article's writing, we aren't on the level of OCaml for type checking and inference, but still, there are a couple of nice things that types with sorbet bring to the table:

Looks like there have been proposals to eliminate use of 3 operand lea in OCaml code (not accepted sadly):

https://github.com/ocaml/ocaml/pull/8531

Haskell and Agda are probably the most obvious examples. Ocaml too, but it is much older, so its type system is not as categorical. There is also Idris, which is not as well-known but is very cool.

That does sound problematic, but without the code it is hard to tell what is the issue. Typically, compiling a 6kLoc file like https://github.com/ocaml/ocaml/blob/trunk/typing/typecore.ml takes 0.8 s on my machine.