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

Many techniques used in OO programming are workarounds for the lack of higher order functions.

This includes a number of the design patterns that are ubiquitous in functional programming. For example, the visitor pattern is a rather complicated way to implement a fold. The workaround is to create a class with methods and pass in an element of the class in as an argument, as a substitute for passing in a function.

The strategy pattern is another example of a scheme that often passes objects as arguments as a substitute for what is actually intended, functions.

Similarly dependency injection often involves some clunky scheme to pass a proxy for functions when it would often be better to simply pass in the functions directly as arguments.

So my answer would be that higher-order functions are often used to perform the same kinds of tasks that OO programmers perform, but directly, and with a lot less boilerplate.