Re: [Chicken-users] Rough proposal for contracts in Chicken

[felix winkelmann]

On 12/19/06, John Cowan <address@hidden> wrote:

> I've read over the PLT Scheme approach, and I think I see how it can be
> adapted to Chicken.  Basically, the syntax of the export declaration is
> extended to provide per-procedure argument and result checking, and a
> new declaration is added to provide module invariants.
>
> [...]
>
> What do you think?

I like this very much. But wouldn't it be better to use a new form, instead
of adding yet more functionality to "declare"? Perhaps a catchall "contract"
macro, that performs per-file declarations (possibly with support by
the compiler, possibly be doing the very (declare (export ...)) behind
the scenes):

;;; some file

(contract
(export
  (plus (-> (number? number?) number?))
  (plus/all (-> (number? . (list-of number?)) number?))
  (exact->div0+mod0 (-> (exact? exact?) (exact? exact?))))
(invariant ...))

...

Hm... there might be better approaches. Anyway, you specified
semantics that look good to me, I just would like to avoid using
"declare" for this purpose.


cheers,
felix