Land of Lisp

Higher-Order Programming

One common stumbling block for programmers learning to write programs in the functional style is that they find it hard to combine different chunks of code to perform a single action. This is called code composition. A programming language should make code composition easy. In other words, it should make it easy for you to take different pieces of code and use them together to solve a task. The most powerful tool for code composition when writing functional code is higher-order programming, which lets you use functions that accept other functions as parameters.

Let’s look at an example to understand why code composition can be a challenge to a beginning functional programmer. Suppose we want to add two to every number in ...