Re: [Caml-list] Why should I use .mli files?

["gallais]

Hi François,

No need to work on big projects to benefit from abstraction: last time
I used an .mli for something else than documentation was when I was
implementing a simulator for a small machine whose memory was an
array of hexadecimal numbers.

After quite a long time spent tracking bugs, I realized that almost all
of them were due to me screwing up the hexadecimal computations.
Fast forward, a module [Hexa] with an abstract type [t] and various
functions such as

from_int: int -> Hexa.t
minus : Hexa.t -> Hexa.t -> Hexa.t
add_int: Hexa.t -> int -> Hexa.t
...

and all my problems were gone: the typechecker was tracking the
use of hexadecimal numbers for me and flagging all operations not
going through these few secure functions as being ill-typed.

That was a nice afternoon.

--
gallais


On 30 October 2012 00:43, Francois Berenger <berenger@riken.jp> wrote:
> 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.
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs