Re: [Caml-list] Compiler feature - useful or not?

[Fernando Alegre <fernando@mail.alemor.org>]

Even better would be to have a "parametrized finite" type. This would
really need to be built into the compiler, as I don't think it can
actually be emulated by either camlp4 or the C interface.

The idea is very simple: add a primitive "n finite" type to the
language, where n is a positive integer constant.

For example:

type bit = 2 finite

type mod3 = 3 finite

Then, fill the type by coercion so that "(x :> n finite)", where both x
and n are known to be constant at compile-time and 0 <= x < n, becomes a
value of type "n finite".

This should be pretty straightforward to implement, and it may simplify
code that depends on types such as "T1 | T2 | T3 | T4"

I don't know how much it would be possible to relax the constraint above
while maintaining the typesystem sound. Does anybody whether this is
a known problem?

Thanks,
Fernando

On Fri, Nov 16, 2007 at 05:43:39PM +0100, Martin Jambon wrote:
> 
> Please don't take my suggestions too seriously, but it could be cool to 
> define types such as:
> 
> type bit = [ 0 | 1 ]