The document outlines a series of topics related to folding in programming, focusing on recursive data structures, definitions of right and left folds, and their relationships with efficiency and duality theorems. It discusses the applications of folds in functions that can be represented in both forms and provides insights into the identity and reverse functions. The series also covers the use of monoids in folding.

1. Decks In The Series (so far)
#1 Folding over recursively defined data structures for natural numbers and lists
#2 Programmatic and mathematical definitions of right fold and left fold
#3 The universal property of fold
#4 For functions that can be defined both as an instance of a right fold and as an instance of a left
fold, one may be more efficient than the other
#5 Folding a list right and left using Cons and Nil results in the identity and reverse functions
#6 Left and right folds and tail recursion
#7 The three duality theorems of fold
#8 Folding with monoids