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From: Markus Mottl <mottl@miss.wu-wien.ac.at>
Message-Id: <200003082229.XAA14210@miss.wu-wien.ac.at>
Subject: Re: additions to standard library?
To: filliatr@csl.sri.com
Date: Wed, 8 Mar 2000 23:29:30 +0100 (MET)
Cc: caml-list@inria.fr (OCAML)
In-Reply-To: <14534.41960.928650.590869@cylinder.csl.sri.com> from "Jean-Christophe Filliatre" at Mar 08, 2000 11:03:04 AM
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> 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