On Tue, Oct 31, 2006 at 07:22:46PM +0100, Michael Sperber wrote:
>
> Aubrey Jaffer <agj_at_alum.mit.edu> writes:
>
> > Why are <= and >= version predicates but < and > are not?
>
> Because I couldn't find an example of a reasonable usage involving the
> latter.
It occurred to me that Debian's apt cache offers a fairly big corpus
of dependency relation examples, and possibly ideas to steal. On a
Debian (or Ubuntu) system with the `grep-dctrl' package installed,
grep-available . -s Package,Depends
lists the dependency relations in the apt cache.
All uses of < and > predicates (<< and >>, in Debian) seem to take the
form
Package: lsb-release
Depends: python (>> 2.3), python (<< 2.5)
indicating that (this version of) lsb-release requires a version of
python strictly greater than 2.3 and strictly less than 2.5. That is,
the following versions match
2.4
2.4.x (for all x)
2.4.x.y (for all x, y)
...
If I understand r5.91rs correctly, this can simply be expressed as
(python 2 4)
All the concrete examples of < and/or > in Debian are along these
lines, i.e. not neede (AIUI) in r6rs.
--
Trent Buck, Student Errant
Received on Tue Oct 31 2006 - 20:56:06 UTC