Re: Should guile-3.0 cond-expand guile-2 and guile-2.2?

[Rob Browning]

Ludovic Courtès <address@hidden> writes:

> Rob Browning <address@hidden> skribis:
>
>>   $ guile-3.0 -c '(display (cond-expand (guile-2.2 "?\n")))
>>   ?
>>
>> Is that intentional?
>
> I think so, though I don’t think this was discussed here.
>
> The way I see it, it means that guile-3 is a superset of 2.2.

OK, though that wasn't true for guile-2.2 with respect to 2.0?  In any
case, it'd be nice to have the policy documented, perhaps on the srfi-0
info page.

At the moment, I just needed a way to write code that behaved
differently with 3.0+ as compared to 2.2, because 2.2 doesn't support
define-module #:re-export-and-replace, and there's no functional
equivalent yet.

For now I did this (I don't currently care about older than 2.2):

  (define (re-export-and-replace! . names)
    (cond-expand
      (guile-3.0
       (module-re-export! (current-module) names #:replace? #t))
      (guile-2.2
       (module-re-export! (current-module) names))
      (else
       (module-re-export! (current-module) names #:replace? #t))))

And migrated all the relevant symbols out of the define-module form.

Do we think that the norm will be for releases to cond-expand the
symbols for all their ancestors (up to some point)?  i.e. guile 4 will
likely cond expand guile-3, guile-3.0, guile-3.1, ... and guile-2,
guile-2.2, and so on?

Thanks
-- 
Rob Browning
rlb @defaultvalue.org and @debian.org
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