smichr/sympy — comment on commit 892ebad6377baacc522f4f3b1dff944db240e961
File:  line 0
By saptman:

To answer your questions, yes, yes, and I am not sure if a disconnected (?) tree is even valid. There are algorithms that can compute the number of components in a disconnected graph but in that case we should treat the tree as a graph rather than as some sort of a heirarchy. Its a good question though but I think that one of the requirements for a graph to be called a tree is that it be connected (ie if there are n nodes then it must have n-1 edges).