On Fri, 10 Mar 2000, Francisco Valverde Albacete wrote:
> Thorsten Ohl wrote:
> 
> > Markus Mottl <mottl@miss.wu-wien.ac.at> writes:
> >
> > > Hello, it sometimes happens that I need functions on abstract data
> >             ^^^^^^^^^ often :-)
> > > types in the standard library which are not available there, but
> > > could be considered as "usual" operations on such data.
> >
> > > Some specific examples include, e.g.:
> >
> > My favorites are Map and List, of which I keep carrying around
> > turbocharged versions.
> 
> Yes... I've done the coding of functional iterators on some dozen ADT
> (written as functors or modules) by now. At first I pretended that they would
> not be necessary but in the end I found I had to code them all, (with all the
> fuss added of making them visible in the signatures of the implementations,
> etc).

>From what I understand, this is what classes and objects are for, though
of course in OCaml there aren't yet polymorphic methods so you lose a lot 
in trying to write extensible ADTs in OCaml this way. If we had
polymorphic methods would that tip the balance in favor of classes for a
utility library? 

> ... snip ...
> 
> PRO: The good thing as X. Leroy stated some time ago is that we do not incur
> in any penalty for such definitions.

I bet a lot of the penalty of OO style could be eliminated if you have a 
compiler that does lots of global analysis, like the SmallEiffel 
compiler. 

> My proposal for now (not the most elegant, I know) would be to add a
> syntactic feature in the language similar to "include" for signatures, but
> effecting textual inclusion of module code, as T.Ohl suggests. Some time ago
> I thought this could be managed by using Camlp4, the caml preprocessor, but
> then the implementor suggested it was hardly used except for Coq and I was
> loath to tackle with it.

That's too bad, I think that some kind of macro approach might be useful
for this problem.

-- Brian