I feel quite dumb! :upside_down_face: I don’t get it with making an .mli for a .ml as a module. I boiled it down to the dumbes … er … simples form of my ignorance. Here is the .ml (in sub-dir lib) let make_point x' y' : point = {x = x'; y = y'} and the corresponding .mli, also in sub-dir lib t…

Yes, that was the confusing (or stunning) point I have/had. Why not keep the usual habbit and place sources in a “source” folder and maybe have any libs that are project-related in there. Placing “bin” and “lib” aside also is strange. The folder “test” should go into sources too. Now, you can have…

[image] yawaramin: At another level you might want to expose a more tightly constrained interface: Have a second .mli with a different name? To increase readability? If someone, as a user, wants to ignore how type ratio looks like, he just can ignore it. And with a more complex module, you e…

That was just an example to show you that there is no definitive single interface for an implementation or vice-versa. In OCaml it’s very important that interfaces and implementations are independent of each other and are not in lockstep. You will see plenty of examples of this as you learn more, eg…

[image] nickm: Why not keep the usual habbit and place sources in a “source” folder and maybe have any libs that are project-related in there. Placing “bin” and “lib” aside also is strange. The folder “test” should go into sources too. I agree that dune init creating a bin/ directory is confu…

I think bin is more of a Unix thing: /bin, /usr/share/bin, and so on. However it would be helpful for the OP to remember that dune models the output project structure as a kind of ‘mirror’ of the source directory structure, so in that context you would be running eg dune exec ./bin/main.exe. Basica…

You are proving my point that bin is not well-known in OCaml circles as a conventional output folder, independent from /usr/bin/ and /bin: build - What are the obj and bin folders (created by Visual Studio) used for? - Stack Overflow You could have exe/ and lib/ folder instead of bin/ and lib/ with…

But my point is that it’s a convention from Unix, not OCaml, as your examples /bin and /usr/bin show. Unix application packages are often laid out with subdirectories lib/, bin/, etc/, that mirror the destinations their files would be installed into finally. So it can make sense if you think of it a…

Granted, and I think we are saying the same thing then. The tradeoffs drawbacks for bin mentioned are having to a) unlearn what that folder means for a percentage (25%?) of devs and b) learn what the Unix filesystem conventions. And the benefits of the status quo are mimicking the Unix-based opam …

[image] yawaramin: So it can make sense if you think of it as trying to lay out the sources in a similar directory structure. Personally I always found it a bit confusing. If a directory has a bin subdirectory I usually expect to find scripts or binary executables in there.

I’ve created PR#2568 that adds text on the role usually assigned to bin, lib and _build folders. I’d love to have your feedback. It touches tutorials Your First OCaml Program , Modules and Libraries With Dune .

Sorry, not getting it with mli

Learning

Topic		Replies	Views
Has there been a syntax proposed for combining .mli into .ml? Ecosystem syntax	27	1578	September 3, 2024
OCaml real pain points Community blog	113	3823	November 26, 2025
Basic problem with Dune and .mli files Ecosystem dune	5	701	November 5, 2023
At what point do you start writing an .mli file? Learning	26	5010	October 25, 2020
A more user-friendly dune Ecosystem	28	932	November 15, 2025

Sorry, not getting it with mli

Related topics