13 Chaining functional tools
In this chapter
- Learn to combine functional tools to do complex queries over data.
- Understand how to replace complex, existing for loops with chains of functional tools.
- Learn how to build data transformation pipelines to do work.
We’ve learned to use the functional tools in isolation to do the work we typically do with for loops over arrays. But as the computation gets more complex, a single functional tool can’t do the job. In this chapter, we will learn how to express complex calculations as a series of steps called a chain. Each step is an application of a functional tool. By combining multiple functional tools together, we can build very complex computations, yet make sure that each step is simple and easy to read and write. This skill is very common among functional programmers. It shows how deep the power of functional tools can get.
The customer communications team continues
Data request: Biggest purchases from our best customers
We suspect that our most loyal customers also make the biggest purchases. We would like to know what the biggest purchase is for each of our best customers (three or more purchases).
Requested by: Chief marketing officer
Owned by: Kim on dev team
Harry: This one seems more complicated.
John: Yeah. We need to get the biggest purchase, but only from the best customers. That sounds hard.