Hi everyone,

Ed Kmett recently pointed me towards his usage of Backpack to write some code in the tagless final style, and I've been playing with it and riffing on it for a while.  There's a solution to the expression problem in there involving classy Prisms (and now Backpacky Prisms)  that seems pretty neat.

I've written it up here:  https://qfpl.io/posts/backpack-for-initial-and-final-encodings/

Hopefully some of you find it interesting.