On Tue, 13 Oct 2009 17:06:26 -0400, John Cowan <[email protected]> wrote:
> Ray Dillinger scripsit:
>
>> It is necessary at times to write modules that do things in different
>> ways depending on what resources they have available. If some module
>> is unavailable, they load some other module and do it a different
>> way instead.
>
> That can be achieved, as I was trying to explain, by loading a shim
> module that is always available and includes one of several sets of
> code, either the Good Module code or an interface to the Bad Module.
> Include is ordinary syntax, so it can be controlled by cond-expand
> or a syntax-rules macro.
Do we really need to require that Core Scheme be able to handle this kind
of thing? In my opinion, it is best handled by expand-time examination of
feature parameters, which is something WG2 can deal with, such as with
META-COND.
Aaron W. Hsu
--
Of all tyrannies, a tyranny sincerely exercised for the good of its
victims may be the most oppressive. -- C. S. Lewis
_______________________________________________
r6rs-discuss mailing list
[email protected]
http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
