A tree is just a graph of a stack over time.
Completely unrelatedly, here‘s Joel on Software on ‘People who are Smart but don’t Get Things Done’:
These kind of people can be identified because they love to point out the theoretical similarity between two widely divergent concepts. For example, they will say, “Spreadsheets are really just a special case of programming language,” and then go off for a week and write a thrilling, brilliant whitepaper about the theoretical computational linguistic attributes of a spreadsheet as a programming language. Smart, but not useful.