The issue you are raising is a good one. SML/NJ can handle some of it,
because the semantics of "open" are different there. Once can actually say:
module Foo = struct
open B
end
and obtain a copy of B within Foo.
This might even work to extend functors as in:
functor Foo(Arg : A) =
struct
module B = Bar(A)
open B
let extensions = ...
end
However, this interpretation of "open" has impacts on compilation
dependencies, in particular scoping analysis (See e.g. "Dependency analysis
for Standard ML; Matthias Blume; ACM Trans. Program. Lang. Syst. 21, 4 (Jul.
1999), Pages 790 - 812").
-Manuel
-----Original Message-----
From: Markus Mottl [mailto:mottl@miss.wu-wien.ac.at]
Sent: Friday, March 10, 2000 12:04 AM
To: caml-redistribution@pauillac.inria.fr
Cc: caml-list@inria.fr
Subject: Re: additions to standard library?
> But when using functorial interfaces like Set.Make, you have to
> redefine these functions for each application of the functor. Thus,
> you really need these functions to be defined in the functor i.e.
> together with the datatype (and, by the way, you can then define these
> functions a bit more efficiently---without using exceptions).
Exactly - this raises another question which has been bothering me from
time to time when using the module system:
How can you extend the functionality of a module without having to "copy"
the definitions of the underlying module "by hand"? In a case which I found
particularly ugly (in the "res"-library), I had to "copy" nearly 100 lines
as in:
module Foo = struct
module B = ...
type t = B.t
...
let iter = B.iter
let iteri = B.iteri
let map = B.map
let mapi = B.mapi
...
end
Everytime the other module gets extended, I have to add code by hand here,
too, to make it available. I do not see any simple workaround for this.
Extending standard libraries with needed functionality would be much easier
if there were a convenient way to get around the problem above.
Regards,
Markus Mottl
-- Markus Mottl, mottl@miss.wu-wien.ac.at, http://miss.wu-wien.ac.at/~mottl
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