Things to learn during this stage that you should remember:
Term rewriting system are a whole topic of research in itself. If you need to be convinced, just look for “term rewriting system” on Google.
A lot of TC-6 is devoted to looking for specific nodes in
lists of nodes, and splitting, and splicing lists at these places. This
could be done by hand, with many hand-written iterations, or using
functors and STL algorithms. You are expected to do the latter,
and to discover things such as
lambda functions, etc.