Re: Restricted Data Types

On Tue, Feb 07, 2006 at 06:38:25PM -0600, Taral wrote:

On 2/5/06, Jim Apple wrote:

...

Have we considered Restricted Data Types?

http://www.cs.chalmers.se/~rjmh/Papers/restricted-datatypes.ps

Or even absracting over contexts, as described in section 7.5 (p. 14/15) of the above?

I've discovered an extra problem with RDT: Context can "appear" from nowhere:

In module Heap: data Ord a => Heap a = ...

In another module: sort :: [a] -> [a] sort = <some code using Heap>

You wanted to mask the constraint, but it will leak into the type signature of "sort", and there's nothing you can do about it, short of some kind of context alias.

But this is exactly the behavior you want, you can't very well expect to sort without an Ord a instance. John -- John Meacham - ⑆repetae.net⑆john⑈