[PPL-devel] How can we detect if PPL is installed

[Mario Mendez]

Hi again!

In the CLIP group (http://clip.dia.fi.upm.es/) we are in the process of 
adding an abstract domain for linear invariants discovery to our static 
analyzer CiaoPP, based on your PPL library. That was the ultimate reason 
for previous questions to the list.

For doing so in a ordered manner, the installation of Ciao now asks the 
user whether PPL is already installed in the computer or not. If it is, 
the Ciao-PPL interface in use is the file 'ppl_ciao.pl'. If not, we 
created a dummy, empty version of it so compilations do not complaint 
about unknown references.

The questions are:
-How can we *automatically* detect if PPL is installed  ->
    Which file can be considered as the reference and which command 
should be used to look for it [rpm -q, install, find...]?
-The location of the Ciao interface can be considered as a constant
DIR_WHERE_PPL_IS_INSTALLED/interfaces/Prolog/Ciao/ppl_ciao.pl
or it depends on any variable (PPL_version,for instance)

Thanks!

Mario