GADTs in Ocaml (was: Private types in 3.11, again)

[Dario Teixeira <darioteixeira@yahoo.com>]

Hi,

> I didn't followed the thread closely, but did you have a look
> at Ocsigen's way to implement params_type?

Thanks for the suggestion.  Actually, there's an Ocsigen connection with
what I'm doing.  The Node module we've been discussing is a simplification;
the real problem is for a data type that can be converted into the XHTML.M
data used in Ocsigen.  (As was discussed some time ago in the Ocsigen mailing
list, the XHTML.M module does not strictly enforce the nested link nodes
rule of the W3C.  Nevertheless I have been looking for a solution that does
enforce this rule).

Anyway, I took a brief look at the code you mentioned, and re-read the
relevant section in the "Rapport Ocsigen" you wrote a while ago (when
I first read that report I had no idea what GADTs were!).  It does seem
that we're all just cooking up workarounds to the lack of GADTs in
Ocaml.  Now, I recall Xavier Leroy mentioning this topic at the user
meeting last year.  It seems the theory is ready, but the compiler
needs some work done before it can accommodate this new feature.  Are
there news on that front?

Best regards,
Dario Teixeira