11 First-class functions: Part 2
In this chapter
- Learn more applications of replace body with callback.
- Understand how returning functions from functions can give functions superpowers.
- Get lots of practice writing higher-order functions to sharpen your skills.
In the last chapter, we learned skills for creating higher-order functions. This chapter will deepen the learning as we apply those skills to more examples. We start by codifying our copy-on-write discipline. We then improve the logging system so it’s not as much work.
One code smell and two refactorings
In the last chapter, we learned a code smell and two refactorings that help us eliminate duplication and find better abstractions. They let us create first-class values and higher-order functions. Just as a reminder, here they are again. We’ll apply these new skills throughout the whole of part 2 of this book. Here they are again for reference.
Code smell: Implicit argument in function name
This code smell identifies aspects of code that could be better expressed as first-class values. If you are referring to a value in the body of a function, and that value is named in the function name, this smell applies. The solution is the next refactoring.
Characteristics
- There are very similar function implementations.
- The name of the function indicates the difference in implementation.
Refactoring: Express implicit argument