A lot has been said about the absence of typeclasses in OCaml (and it’s sibling F#), but I haven’t been able to find any good resources explaining why the OCaml’s developers felt those are not needed. I did find F#'s creator’s reasoning against them here , and I assume the same line of reasoning app…

I don’t have the impression the the devs did not think such stuff is not needed. It’s been discussed in great detail for a long time. Problem is, it’s very very complex.

I am a bit more interested in the foundational reasoning to avoid them in the first place, but it’s nice to see that the maintainers are looking into some potential solutions the problem. Sadly, it seems the idea of modular implicits didn’t get far. I wonder if this is still in the cards or it got …

Hello @bbatsov , I am not an expert but as @yawaramin commented, this topic has been discussed in the community in the context of modular implicits . For example here . But it seems to be not easy to introduce. On the other side, there were discussed ways to “emulate type-classes” (whatever it means)…

[image] bbatsov: I am a bit more interested in the foundational reasoning to avoid them in the first place, I guess because OCaml and its ancestors (Caml Light, Caml, ML) more or less predate type classes, or at the very least when OCaml was created type classes were still experimental and un…

[image] bbatsov: I am a bit more interested in the foundational reasoning to avoid them in the first place First, I’m an advocate of typeclasses – after using Rust’s traits, I think their value is -immense-. But there is a good and valid argument to be made, that typeclasses can produce hard…

[image] bbatsov: I get that any form of type-level programming comes with a certain degree of complexity, but I also find it somewhat frustrating that basic things like printing some data for debug purposes require you to either hand-roll some print function or use ppx. The inability to overload…

I think this is correct. My memory is a little shaky, but I recall looking at the generated raw code for debug-printing, close to when the Rust compiler gets it (and after macro-expansion). One can see that debug-printing uses the Rust typeclass machinery to generate the per-argument print functio…

I would like to emphasize that these two issues are really orthogonal: “printing some data for debug purposes” is about defining new functions, while “overloading operators” is about figuring out which existing functions to use at a given type. I get your point, but there’s also the take that the…

[image] Chet_Murthy: With OCaml today, you can read a bit of code, and if you know where all the names in it come from (and you can figure that out in a straightforward way), then you know what the code does. There are no “hidden names” that you can only get access to if you know how the typeche…

Why doesn't OCaml have typeclasses (or something similar)?

Learning

yawaramin July 15, 2025, 7:56pm 3

See Modular Implicits - #9 by gasche

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Why doesn't OCaml have typeclasses (or something similar)?

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