mlton VS ocaml

https://github.com/MLton/mlton/issues/473

Is there sufficient use of MLTon "native" backend out there to consider it mature? or Do people prefer the LLVM or C backend instead in general?

Once I got the parser ready in OCaml, I thought I port it to Standard ML, since it belong to the same ML language family. I was also curious on how well mlton could optimise it. The language lacks custom let bindings, so I resorted to use Result.bind manually. This makes code much less readable and more verbose. The standard library also lacks result type, so I had to come up with my own simple implementation. There's also a lack of any hash map in the standard library, so I just used a list of key-value pairs. This isn't correct, but it's the closest I could get without inventing my own hash map. MLton's compile times are slow. It also lacks interactive REPL. Because of that I used alternative Standard ML implementation for interactive usage: PolyML. Debugging MLton binaries is also pretty hard. gdb doesn't work and there's no bundled debugger. I had to resort to debugging facilities built into PolyML. Valgrind doesn't work with mlton binaries, as it doesn't report any memory allocations. Looks like mlton uses mmap for allocation memory. Surprisingly, performance is not the best. This might be due to heavy usage of my custom Result type and bind calls. Exceptions seem to be a more natural choice for error reporting in Standard ML. I tried to make such a change, but this didn't improve the performance much.

MLton

Something I’d highly recommend you do before concluding that SML’s module system is the best is to go through and read the MLton Basis library. MLton uses the module system extremely heavily in its definition of the standard, and I think it’s extremely important to understand what you may be getting yourself into when you add those features, and what you may lose in return.

If you’re fine with tracing GC (which depends on the situation, of course), Standard ML is a perfectly boring language (that IIUC predated and inspired Caml) and MLton[1] is a very nice optimizing compiler for it. The language is awkward at times (in particular, the separate sublanguage of modules can be downright unwieldy), and the library has some of the usual blind spots such as nonexistent Unicode support (well, not every language WG is allocated a John Cowan).

Speaking of, Scheme can also be a delightful unexciting static language; consider for example the C-producing implementation Chicken[2]. The pattern-matching / algebraic-datatype story was still rather unsatisfying last I checked, but there are other situations where it shines—it’s complementary to SML in a way.

You’re not going to be writing a kernel or a real-time renderer in either (though I’m certain people have taken that as a challenge), they son’t afford the flashy EDSLs of Tcl, Ruby, or Racket, and I can’t say I can prototype in them like I do in Python or sh+tools, but there is a comfortable middle ground where they fit well. (I hear others use Go in what seem like the same places, but to me it feels so thin and devoid of joy that I can’t really compare.)

The FFI tools in both of the mentioned implementations are excellent, though not quite at the “type in C declarations” level of LuaJIT and D.

[1] http://mlton.org/

[2] https://call-cc.org/

Unfortunately, I haven't found a ton of "easily-digestible" and, at the same time, comprehensive guides on compiling functional languages. Generally you'll find a mix of blog posts/class notes/papers covering a single step.

Some resources I like:

- Andrew Kennedy's 2007 paper Compiling with Continuations, Continued [1]. This one is the most clear IMO

- Andrew Appel's Compiling with Continuations book (a bit outdated though... assembly code is for VAX)

- Matt Might's series [2]

- MLton's source and documentation [3]

[1] https://www.microsoft.com/en-us/research/wp-content/uploads/...

[2] https://matt.might.net/articles/closure-conversion/

[3] http://mlton.org/

More broadly, they can be fast even without such extensions if they aggressively pursue optimization opportunities afforded by static typing, like MLton for example, but that also impacts compilation performance negatively.

https://github.com/MLton/mlton/blob/master/lib/mlton/basic/hash-set.sig https://github.com/MLton/mlton/blob/master/lib/mlton/basic/hash-table.sig

> 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

> 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

An amazing example is Ocaml lang logo / mascot. It might be useful to talk with them to know what was the process behind this work. The About page camel head on Perl dot org header is also a pretty good example of simplification, but it's not a logo, just a friendly illustration, as the O'Reilly camel is. Another notable logo for this animal is the well known tobacco industry company, but don't get me started on that (“good” logo, though, if we look at the effectiveness of their marketing).

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.