As I just realized, I 'reinvented' Evan's Focus library and he's done a great job at giving an introduction.
A quick comparison to what this library handles differently:
Accessors are just aliases for functions, libraries can provide
Accessors without actually depending on this library!
Meanwhile I decided to use Evan's library for my simple purposes. I'll upload this library anyway, only to give others polymorphic lenses if they need them.
Accessors are just generalized getters and setters for arbitrary structures and their parts. This aims to be a simple version of lenses.