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

[Andreas Rossberg <rossberg@mpi-sws.org>]

On Nov 1, 2012, at 03.44 h, Jacques Garrigue wrote:
> Wow.
> I see that a big debate is going on mli files and declarations
> inside ml files.
>
> I think that lots of people have given this problem a lot of thought
> during many years.
>
> [...]
>
> Now, is maintaining mli files really painful?
> In my experience, not at all.

I strongly second that. Separation of interface and implementation _is  
a feature_! In fact, it is one of the high marks of ML modules (as  
opposed to, say, privacy in Java classes, let alone the mess that is C/ 
C++ style header files). Its semantics is simple but powerful.

The separation improves modularity by naturally encouraging  
abstraction, low coupling, and documentation. Better modularity makes  
for better maintainability. And the separation makes code more  
readable -- which, as others have noted, is 10 times more important  
than making it more writable, for anything but trivial projects (i.e.,  
anything where modules are actually needed).

No doubt you can find cases where the redundancy is unfortunate.  
Mainly these are ones involving larger data type definitions that  
refer to abstract types from the same module, and hence cannot easily  
be factored out into a separate module. But in my experience, such  
cases are rare, and the minor inconvenience is far outweighed by the  
overall benefits.

/Andreas