This is a commonly requested feature. One issue is that a file a.ml creates a module A. However, a file a.mli does not create a module type A. I'm not sure why this is the case. Does anyone know if there is a specific reason?


On Fri, Apr 17, 2009 at 4:51 PM, Peter Hawkins <hawkinsp@cs.stanford.edu> wrote:
Hi...

I have a quick question. I want to extend the List module with various
functions that I want that aren't present in the standard library,
much as the Batteries ExtList library does.

I might write the following code in "mylibrary.ml":
module MyList = struct
 include List
 let foo x = ... code here
 let bar y = ... code here
end

That's ok so far, but now suppose I want to write a "mylibrary.mli"
interface file corresponding to "mylibrary.ml". Ideally I'd write
something like this in "mylibrary.mli":
module MyList : sig
 include List  (* unknown module type List *)
 val foo : ...
 val bar : ...
end

Unfortunately I can't include "List" here since it is a structure, not
a signature. I don't think there is a way to say "include the
signature associated with List".

I can think of three solutions:
a) Copy the complete signature of List into MyList. This is a bad idea
since the List module might change in the future. This is what the
Batteries ExtList module does.
b) Alter the List module to define a signature, say List.S, in
addition to its other contents. I can't easily do this since I didn't
write the List module.
c) Don't write a .mli file at all.

Are there any other alternatives?

Cheers,
Peter

_______________________________________________
Caml-list mailing list. Subscription management:
http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
Archives: http://caml.inria.fr
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs