regression of is_isomorphic in 5.16.1 for empty (di)graphs



Hi,

the error I've reported seems to have been fixed now,
but it seems another (likely small) error crept in:

(%i1) load(graphs);
(%i2) is_isomorphic(path_digraph(0),path_digraph(0));
(%o2) false
(%i3) is_isomorphic(path_graph(0),path_graph(0));
(%o3) false

(this with 5.16.1; using non-empty vertex sets it seems to work now).

So apparently some triviality condition has been overlooked (all these cases
worked with 5.15.0).

Oliver

-- 
Dr. Oliver Kullmann
Computer Science Department
Swansea University
Faraday Building, Singleton Park
Swansea SA2 8PP, UK
http://cs.swan.ac.uk/~csoliver/