Deriving a polymorphic mapping module

Deriving a polymorphic mapping module

[Mike Spivey]

Given the functor-based Map module in the standard library of OCaml,
is there any way of defining polymorphic mappings, like the old module
provided with Caml Light, that has a polymorphic interface and always
uses the polymorphic compare function?  If not, then this seems to me
to be a weakness in the module system.

Looking at the Hashtbl module, I see that it in fact contains two
completely independent implementations of hash tables, one polymorphic
and one using a functor, so I guess the answer is 'no'.

-- Mike Spivey

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Mauvaise traduction francaise:

Etant donne la module Map du bibliotheque standardise de OCaml,
existe-t-il aucune facon de definer des mappings polymorphes, comme
l'ancien module map de Caml Light, qui a une interface polymorphe, et
utilise toujours la fonction compare polymorphe?  Si ca n'existe pas,
ce me semble une faiblesse de la systeme de modules.

En regardant la module Hashtbl, je vois qu'il contient en effet deux
implantations des hash tables, l'une polymorphe et l'autre basee sur
un functor.  Donc, je crois que la reponse est 'non'.

Re: Deriving a polymorphic mapping module

[Benoit de Boursetty]

Hi,

On Thu, 9 Dec 1999, Mike Spivey wrote:

> Given the functor-based Map module in the standard library of OCaml,
> is there any way of defining polymorphic mappings, like the old module
> provided with Caml Light, that has a polymorphic interface and always
> uses the polymorphic compare function?  If not, then this seems to me
> to be a weakness in the module system.

The same problem has already occured for me, with the Set module.
A change of typing resolves the problem. You can find solutions for Set
and Map at

http://www.stud.enst.fr/~debourse/caml.html

Benoit de Boursetty.