[r6rs-discuss] Library version numbers

[Trent Buck]

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