Higher-order functions are the ultimate solution to DRY. In this lecture we introduce a number of standard higher-order functions over lists, functions for creating and manipulating other functions.

Jam Session

Erratum: 10.59

The correct steps of the derivation presented in the slides are the following:

mul x y = \s z -> x (y s) z

= \s z -> (x . y) s z

= x . y