My attempt to work through the various type systems as detailed in Pierce's Types and Programming Languages.

Doubtless of zero interest to anyone else but me, this wip is just for my own practice. Check again in 5 years time to see it finished.

I've experimented with various libraries and approaches here, so please do not look at this as the best (or even a good) way of implementing any of these type systems: the code style is not consistent!

This is also used as a storage place for various bits of Agda related to type theory.