[spqr233]

I don't the author really gave Ocaml a chance. He argues that every language needs to have interfaces. I agree somewhat with that statement, but I think the truer statement is to say that every language needs to have some way of defining composition at a structural level.

An interface allows you to pass different "structures" to the same function so long as they adhere to the same spec. In Ocaml this is accomplished through modules, functors, and module signatures. Ocaml's module signature can play the same exact role as interfaces in Haskell, Rust or F#.

The module system is arguably more expressive than what can be accomplished to interfaces. To give an example, Ocaml suffers from the same problem as rust does with having two standard implementations of a async runtime. Just like rusts: tokio and async-std, ocaml has Lwt, Async, (and newly added to the mix Eio).

Whereas in rust most libraries just implement one of these systems, and you'll have to use compiler directives to support both. Ocaml's module system means that you can describe the async runtime as a signature and make your entire library generic to the async runtime it runs on top of. Most of the well-used libraries do this, and so you don't have to worry too much about which runtime you decide to use.

Clearly, a language that can do that must have in some place a system that can replace interfaces.

[hardwaregeek]

Politely, I feel like this is the issue with OCaml as a community. You gave a beautiful answer about programming language design and composition. But how does it feel to write the language? How can you print a user defined data type? From reading around, it seems like your options are: explicitly pass a print function for that specific type, use a third party library for printing, or (my "favorite") don't. Or how does it feel to write a function that takes a generic that can be printed, checked for equality, and read? Or to convert one type into another type?

And we're still talking about semantics here. How does it feel to use the language server? How does it feel to read the code? To build the language? Ultimately that's what users judge a language on. Yes, Rust in some ways has a worse form of abstraction. It is global, not fully generic and doesn't allow for overloading. But it creates a user experience that is nicer. It lets a user print something and compare two variables and do type conversions without having to scratch their head, read a forum post and import a library.

[ywei3410]

> You gave a beautiful answer about programming language

You do the same thing as in Rust, Scala or Haskell and derive the printer [1]. Then at the callsite, if you know the type then you do `T.show` to print it or `T.eq`. If you don't know the type, then you pass it in at the top level as a module and then do `T.show` or `T.eq`.

> Or to convert one type into another type?

If you want to convert a type, then you have a type that you want to convert from such as foo and bar, then you do `Foo.to_bar value`.

We can keep going, but you can get the point.

You _can't_ judge a language by doing what you want to do with one language in another. If I judge Rust by writing recursive data structures and complaining about performance and verbosity that's not particularly fair correct? I can't say that Dart is terrible for desktop because I can't use chrome developer tools on its canvas output and ignore it's hot-reloading server. I can't say Common Lisp code is unreadable because I don't have type annotations and ignore the REPL for introspection.

[1] https://github.com/ocaml-ppx/ppx_deriving

[hardwaregeek]

Okay...so you have to add a third party library to print? Yes, recursive data structures are a pain in Rust (well, recursive multi-owner data structures). But that's like comparing changing your oil to opening your car door. We do one of these a lot more. And bear in mind, I had to find this answer by googling and reading a random forum post. That's some pretty poor documentation.

And that's not talking about aesthetics. `T.show foo` or `Foo.to_bar value` is a lot of syntactic overhead for a rather common task.

And again, these are the lesser concerns to the other ones I outlined. Reading the code, building the code, and understanding the compiler errors are the big ones.

[ywei3410]

Not really third-party; ocaml-ppx is something similar to `javax` in the Java space? But it is optional and doesn't come bundled with OCaml.

Recursive structures are only rare in Rust _because_ they suck to write and have terrible performance characteristics in the language. In languages like Haskell, OCaml and Scala using tagless initial encodings for eDSL's [2] are really, really common.

I don't write Rust like I write any semi-functional language with function composition because, well, it's _painful_ and not a good fit for the language.

> `T.show foo` or `Foo.to_bar value` is a lot of syntactic overhead

The `T.()` opens a scope so OCaml code generally looks like:

``` let foo = T.(if equal zero x then show x else "not here") ```

for,

``` fn foo(t: T) -> String { if(t == T::ZERO) { t.show() } else { "not here".into() } } ```

Even when talking about usage, each language community for better or worse has a predefined workflow in mind. Your questions and workflow are specific to a particular language; you don't, for example, ask about the REPL, the compile times, debugging macros, the cold-start of the compiler, whether hot-reloading is a thing, the debugger, how it interacts with perf, how to instrument an application. Presumably because the language you use or the programs that you make don't have those components as part of their main workflow.

[1] https://github.com/ocaml-ppx [2] https://peddie.github.io/encodings/encodings-text.html

[hardwaregeek]

A lot of these things that you mentioned are valid flaws in Rust. I'm not going to dismiss them as not important or non-problems because they are genuine issues. Compile times suck. We could use hot reloading and a REPL. Debugging macros, instrumentation and perf stuff is good, but I assume it could be better. That's what I expect from a language community. Not constant denial about the state of usability. And it really does feel like many of the smaller language communities fall into this hive-mind where type signatures are valid documentation and who needs to use an editor other than emacs?

[ywei3410]

They are genuine issues, within Rust, but the way you /categorize/ the severity of the issue is different within language communities. They don't impact usability /much/ because of Rust's community, focus, size and niche.

Compile times in Rust are a problem, but the RLS does a good enough job of feedback and the development loop happens enough in compile time, that users don't miss it enough, compared to, say, Java which relies heavily on runtime behaviour/reflection for application behaviour.

Debugging token macros could be better, such as with a better macro-stepper, but you don't write enough macros in Rust to care heavily about it to make it a big deal, unlike in a Lisp.

Hot reloading would be nice, but not and ~essential~ part of development and deployment like in BEAM. Better reflection utilities might be nice but I doubt Rust libraries will ever be heavily dependent on it in the same way that Go or Java are.

[yawaramin]

If you are referring to OCaml, many people in the community care a lot about writing good documentation so that it's not just the type signatures. In fact the OCaml website team have made amazing leaps and strides integrating package documentation directly in the website.

And the experience using OCaml LSP Server with VSCode nowadays is honestly pretty good--type annotations displayed, error messages, go to definition, generating interface files. The core functionality is all there.

[yawaramin]

You don't need a third-party library to derive a pretty-printer for your types, it just makes it simpler. OCaml takes the approach that the core compiler doesn't do any codegen, that is left to PPXs (basically, middlewares which transform code) which run before the compiler.

You can write a pretty-printer yourself using the conventions of the `Format` module. Is it manual and annoying? Yeah. That's why the PPX exists. It's a tradeoff.

[yodsanklai]

> `T.show foo` or `Foo.to_bar value` is a lot of syntactic overhead for a rather common task.

A lot of syntactic overhead sounds like a stretch. I suppose you could drop the `T` like you do in Haskell but I personally like my language to be a bit more explicit. It improves readability.

[agumonkey]

People have to realize that printing is the least of your concern. Visible representation is not solving problem.

[pdhborges]

Scala is probably not a good example because if you need some quick and dirty printing you can override toString and keep the rest of the generic code intact. In OCaml, Rust and Haskell you would have to add type constraints in a bunch of places to make println! T.to_string and show work.

[yodsanklai]

> How can you print a user defined data type?

Pretty much the same way you'd do in Haskell or Rust: you add a `[@@deriving show]` directive to your datatype.

[v0idzer0]

Came here to make this exact point. But I totally agree with all of his other complaints. It’s a good list of the cons, but ignored the many pros

[boxed]

To me it seems he gave it a lot of chance in order to find this many problems.

It does sound to me like you stopped reading after the first point. Maybe you didn't give the post a chance?

[WastingMyTime89]

To be honest, anyone who used Ocaml understands immediately that the author gave it no chance and went looking for problems. It’s obvious because the post lingers a lot about things which are not actually issues like type conversion but don’t talk about the very real issues Ocaml has (opam is not great, dune is weird).

[hardwaregeek]

Why are these things not issues? I think it's totally valid for someone who doesn't understand OCaml to raise issues of usability or documentation. It's not just the issues of experts that are a concern. And it's very demoralizing to get a "you're holding it wrong" response to a complaint.

[WastingMyTime89]

Because they are not issues on a day to day basis when you use the language.

I used Ocaml for a paid internship some years ago. I was very much a beginner. Do you know how many time I felt at loss or annoyed by type conversion or the precedence rules for various part of the syntax? I never did.

The truth is you never encounter the precedence rules when writing Ocaml normally using parentheses like a normal human being and you don’t convert that much between exotic types. Most of the conversion you actually do are between the same types and most of the time you have to write converter anyway because there is logic involved. I worked professionally as a Java developer for a bit. I think I had to write more conversion code between weird classes then than I ever did in Ocaml.

The issue is not telling people they are "holding it wrong". The issue is that this is not what’s going to annoy you as an Ocaml beginner.

The author of this article is not even an Ocaml beginner by the way. That’s actually someone who used to work on the Haskell compiler.

[ModernMech]

> The issue is that this is not what’s going to annoy you as an Ocaml beginner.

Sure, but tbf, the post is about what annoys the author, not what would annoy beginners. As you say, the author is not a beginner, and so their problems wouldn't be beginner problems.

[WastingMyTime89]

That’s not the point I was making. They are not expert problems either. How often as an expert do you think you encounter precedence issues you were not encountering as a beginner?

[illiarian]

> Because they are not issues on a day to day basis when you use the language.

They still are. You just internalize them. Progammers are the world's greatest masochists with the world's biggest Stockholm syndromes, and we don't like to admit it.

For example, his pain points about syntax ambiguity are absolutely valid, and true. However, when you "use the language every day" you learn to avoid those constructs and extract them into separate functions for example because "that's how it's always done, and it's a nice little quirk of the language".

[WastingMyTime89]

No, the syntax parts he criticises are not this kind (they are not ambiguous by the way). What’s in the article is very unidiomatic OCaml incorrectly intended purposefully to make it look like it’s doing something else than what it does.

You don’t write tuples without parentheses because it’s weird, harder to read and no one does it. Same for the precedence rules of expression. You just use begin and end for blocks like you would use braces in C because you actually want to write a block. No one is just randomly writing nested code without them because well it doesn’t work.

It’s not a quirk. The author is just complaining that you have to mark blocks like in every language. That’s a weird thing to complain about.

I agree that the lack of as-hoc polymorphism is a downside (I don’t agree with how the article presents it but the article is disingenuous from the start anyway). Everyone would like to have modular implicit.

[boxed]

It sounds like it's weird and annoying to convert a value to a string. That's pretty damning. Did I misunderstand?

[belmont_sup]

If Ocaml fixes this and makes opam/dune play in the same field as cargo, life would be great as an ocaml programmer.

Sometimes I go back to F# and sigh because I can just print any complex data structure. Sure, there’re limits, but it’s just one less pain.

Regardless, really enjoy everything else. I cloned and built the Dune repo to try to help fix something. Compiled very quickly for its size.

[hajile]

Primitive conversions are as simple as `<type>_of_<newType>(myValue)`. For example, `int_of_float(2.0)` will give you an integer. `string_of_int(123)` will return a string. Noting very surprising.

If you want to do more complex conversions, you have to write those functions and call them.

I don't much care for Ocaml syntax (StandardML is a better language in basically every way and ReasonML is Ocaml with better syntax), but this isn't a big deal.

[boxed]

That's terrible though. How can that possibly work if the type is not hardcoded? How can you write code that works on any type like that?

[hajile]

The type system will know if you don't handle a potential conversion.

This restriction is better for pretty much every real-world use case anyway.

If you don't know what you're converting, then you are almost guaranteed to be getting garbage out the other end. If you do know what you are converting, being explicit and covering all your options isn't a big deal.

And of course, you can pack this all away in a module if you really want too. Modules are more flexible than typeclasses in a language like Haskell anyway (as you can't have multiple typeclass definitions in Haskell).

In truth, I believe module typeclasses (typeclasses only definable in modules) would be a nice addition. It would allow flexibility while creating a pattern that actively discourages the abuse you see in Haskell where typeclasses quickly devolve into unreadable garbage.

[GeorgeWBasic]

I've been using opam and dune for a few years now and they haven't annoyed me much since I got used to how to set up projects. What are the issues with them?

[spqr233]

It's more that only really strongly disagreed with that point. Frankly, there are some cons with using Ocaml. In practice, I think the library support for ocaml isn't completely there given the small community.

[maleldil]

> Ocaml's module system means that you can describe the async runtime as a signature and make your entire library generic to the async runtime it runs on top of

Is this the program describing the interface it expects, and the compiler matching that with the implementations structure (e.g. Go interfaces, Python Protocols), or is it something someone declares and the libraries implement?

[yawaramin]

Mostly the former. The compiler infers the type of the implementation and ensures it conforms to the interface. But, you can further restrict the interface's type to hide details from the outside world.

[actionfromafar]

> Ocaml's module system means that you can describe the async runtime as a signature and make your entire library generic to the async runtime it runs on top of

So ... can you ELI5 to me how that is different from how you can for instance compile a C program against different libc implementations?

[kajaktum]

I mean…you can technically have a function that take void* and return void* be the interface. But you wouldn’t be able to represent things like iterator and chain them together without care. In C you would be tripping all over the slight details like forgetting to check errno or something.

[actionfromafar]

So, it's like C++20 then?