This package is a playground full of comonadic folds.
This style of fold is documented in <https://www.fpcomplete.com/user/edwardk/cellular-automata/part-2 "Cellular Automata, Part II: PNGs and Moore">
This package can be seen as what happens if you chase Max Rabkin's <http://squing.blogspot.com/2008/11/beautiful-folding.html "Beautiful Folding"> to its logical conclusion.
More information on this approach can be found in the <http://conal.net/blog/posts/another-lovely-example-of-type-class-morphisms "Another lovely example of type class morphisms"> and <http://conal.net/blog/posts/more-beautiful-fold-zipping "More beautiful fold zipping"> posts by Conal Elliott, as well as in Gabriel Gonzales' <http://www.haskellforall.com/2013/08/composable-streaming-folds.html "Composable Streaming Folds">.