[082349872349872]

I'd agree with TFA that canonical Huffman, although interesting, would be yet another thing to explain, and better left out of scope, but it does raise a question:

In what other areas (there must be many) do we use trees in principle but sequences in practice?

(eg code: we think of it as a tree, yet we store source as a string and run executables which —at least when statically linked— are also stored as strings)

[mxmlnkn]

> In what other areas (there must be many) do we use trees in principle but sequences in practice?

Heapsort comes to mind first.