This is a pretty neat approach to parsing by hand, and it's probably helpful to build intuition about LR. Basically if you give an explanation of LR including shifts and reduces, then you can show how that maps to the hand-written parser (i.e. the `_cont` functions are shifts that eventually result in a reduce when they return and use the parameter that they were passed).

Shameless self-plug, in case you want to understand more about LR parsing: https://www.youtube.com/watch?v=8UDWd-Axd5A