[r6rs-discuss] Why can ... and _ not be literals?

From: AndrevanTonder <andre>
Date: Tue, 26 Jun 2007 22:22:00 -0400 (EDT)

On Tue, 26 Jun 2007, David Van Horn wrote:

> On 6/26/07, AndrevanTonder <andre at het.brown.edu> wrote:
>> On Tue, 26 Jun 2007, David Van Horn wrote:
>>
>> > On 6/25/07, AndrevanTonder <andre at het.brown.edu> wrote:
>> >> There is in fact a trivial solution to porting legacy macros
>> >> using underscore. Simply put them in a library where you use
>> >>
>> >> (import (except (r6rs base) _))
>> >
>> > Isn't this a syntax violation? This excludes `_' from (meta 0),
>> > implicitly, but (r6rs base) provides `_' only at (meta 1).
>>
>> No - it excludes _ from all meta-levels at which (r6rs base) would have
>> otherwise provided it [...].
>
> Sorry, I'm clearly misunderstanding something in the draft. Can you
> point out where this is specified?

The following paragraph in 6.2 at least partially answers th question, I think:

The level for each imported binding is determined by the enclosing for form of
the import in the importing library, in addition to the levels of the identifier
in the exporting library. Import and export levels are combined by pairwise
addition of all level combinations.

Andre
Received on Tue Jun 26 2007 - 22:22:00 UTC