What are some interesting uses of higher-order functions?

Question

I\'m currently doing a Functional Programming course and I\'m quite amused by the concept of higher-order functions and functions as first class citizens. However, I can\'t yet

Answer 1

One thing that's kind of fun, if not particularly practical, is Church Numerals. It's a way of representing integers using nothing but functions. Crazy, I know. Here's an implementation in JavaScript that I made. It might be easier to understand than a Lisp/Haskell implementation. (But probably not, to be honest. JavaScript wasn't really meant for this kind of thing.)