I’m trying to reimplement this simple example of how to use traits (Rust) but in OCaml. I thought functors would be the way to go but I’m not getting far going that route. I went asking and hear that functors are actually not very common to write day-to-day ( response to my question on X ). If that’s …

[image] c-cube: let content : (module Summary) list = [ (module (val news_article : News_article) : Summary) ] OMG THIS WORKED!!! :partying_face:

Simple example: type out_stream = { output: string -> unit; flush: unit -> unit; close: unit -> unit } let out_of_buf (buf:Buffer.t) : out_stream = { output = Buffer.add_string buf; flush = ignore; close=ignore } let out_of_unix_fd (fd:Unix.file_descr) : out_stream = { (* note: the…

I find Unison’s new OCaml version-agnostic serialization module a really cool example of this kind of modelling: https://github.com/bcpierce00/unison/blob/master/src/ubase/umarshal.ml

In OOP, you could have classes taking different data through their constructors while implementing the same interface, and I’ve found that partial application enables more or less the same thing in FP. (* A record taking a function that modifies a string. *) type t = { f_modify_string : string -> s…

[image] c-cube: Eio used to use that and an early post about it had a nice rationale about why objects were used Indeed, If you don’t mind static type checking, it’s a solution. :wink:

People who write OCaml are generally fine with static type checking :^)

Wait and see. If it seems correct in theory, it’s not as obvious in practice. As soon as you pack your value in an existential type (aka object) you’re loosing statically any type information you have. And so, you end up with a DSL with only one type. There is a blog post from a SML maintainer, tha…

Was it this one? Dynamic Languages are Static Languages | Existential Type

That’s a great post but, yes, it’s the whole point: you want a single type to stand for multiple concrete types because you are abstracting. There’s no link to dynamic typing, you still get full type safety at the granularity you prefer. Static typing doesn’t mean static dispatch, thankfully. It’d …

Indeed, it was the article I had in mind.

What's the OCaml way to do multiple interfaces?

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What's the OCaml way to do multiple interfaces?

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