Thinking about it, there's at least one case where mli files are not so
useful: When you have several modules which must all comply with a certain
module type. In that case, all the mli files would be identical, and a
modification of the module type would necessitate to change all the .mli.
What would be the best way to handle that situation?
I was thinking of making an inner module, coerce it to the desired type,
and open it afterwards, but the resulting module would still have a ref to
the inner module in its type.

E.g.:

in the file mymodule.ml

-----------------------8<-------------------

module Inner = (
struct

  (* implementation *)

end : Sig)

open Inner

-----------------------8<-------------------

and the file sig.mli would be the required module type.

didier

2012/10/30 Francois Berenger <berenger@riken.jp>

> Hello,
>
> Here is my stupid question of the day:
> what's the use of those .mli files?
>
> Is it just to separate interface from implementation
> so that the implementation of a module can be changed
> without clients of its interface to have to bother?
>
> Does it make compilation of large software faster
> by allowing for more parallelization and maybe later on avoiding to
> recompile some parts?
>
> Usually I program in a pure functional style, so my modules
> don't carry an internal state.
> I feel like "if someone want to re-use a function, so be it".
> If I really want to hide a function that I am afraid people
> may call in an incorrect manner, I declare it internally
> to some public function and use it correctly.
>
> Also, maybe I only work on toy-size OCaml projects. So, I never bothrered
> to create any .mli file.
> I would like to know if I should bother about them.
>
> Thanks a lot,
> Francois.
>
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