Checking if a given port is installed in pre-fetch

[Adam Mercer]

On Sun, Mar 2, 2008 at 12:16 PM, Daniel J. Luke <dluke at geeklair.net> wrote:

>  You can do almost anything from within a portfile, but there are lots
>  of things that you maybe shouldn't.
>
>  What are you trying to accomplish?

I want to upgrade the science/geos port to 3.0.0 but
matplotlib-basemap requires geos-2.2.3 and will not work with
geos-3.0.0. Unfortunately it doesn't appear possible to install both
geos-2.2.3 and geos-3.0.0 at the the same time, so I was wondering if
there was a way that I could make a port for each version and mark
them as conflicting?

Cheers

Adam