Thanks.

Your notes are very appreciated and useful.


2) Standard c++ has a std::rel_ops namespace. This allows you to define all of the other relational operators without you having to write any extra code, given that you've defined operator < and operator =.
Good!

Well, what if this class is used from several threads and each thread wants a different sort order at the same time? Disaster!
Upssss, good note!

Very thanks!!