A few weeks ago I made a presentation to the Philadelphia Perlmongers
(http://thenceforward.net/perl/talks/phlpm20180312/index.html) on the
subject "Testing CPAN against the Perl 5 Core Distribution: Where Do We
Stand?". In that presentation, I sketched the concept of the CPAN river
and described it as a directed acyclic graph (DAG)
(http://thenceforward.net/perl/talks/phlpm20180312/slide017.html), using
one of Neil Bower's images to make that point.
In the discussion afterwards, a prominent former COBOL programmer
suggested that there was nothing to exclude the possibility of circular
dependencies among CPAN distributions. A could depend on B, which
depends on C, which depends on A. If so, we would have a cyclic graph.
Wouldn't that undermine the concept of the CPAN river, he asked.
Since all I know about DAGs I got from reading Wikipedia and the
documentation to Jarkko's Graph.pm module, I didn't have a good
response. So I promised to ask the question here.
* Can CPAN be cyclic?
* If so, then does that mean that, when we speak of CPAN as a river, we
are *imposing* DAG-ness on it by means of the algorithm(s) with which we
calculate the river (e.g., https://github.com/dagolden/zzz-index-cpan-meta)?
Thank you very much.
Jim Keenan
