5.10 Summary

In this chapter, we have seen two reductions that are higher-order functions: max() and min(). We looked at the two central higher-order functions, map() and filter(). We also looked at sorted().

In addition, we looked at how to use a higher-order function to transform the structure of data. We can perform several common transformations, including wrapping, unwrapping, flattening, and structuring sequences of different kinds.

We looked at two ways to define our own higher-order functions, which are as follows:

• The def statement. Similar to a lambda form that we assign to a variable.

• Defining a callable class as a kind of function that emits composite functions.

We can also use decorators to emit composite functions. We’ll return to this in Chapter 12, Decorator Design Techniques.

In the next chapter, we’ll look at the idea of purely functional iteration via recursion. We’ll use Pythonic structures to make several common improvements over purely...