Posted on May 25, 2018

This is a very small chapter (just one page) in the book, and all we do here is define a permutation, introduce some notation, and count the total number of permutations of a given number of objects (everyone knows the answer). Nevertheless, we need to tell Haskell what a set is before we can tell it what a permutation is. And then we can also define some of the familiar operations on sets, which may come in handy later. ...