ABSTRACT
In chapter 10 we’ll discuss function factories. A function factory is a function that makes functions.
Of the three main functional programming tools (functionals, function factories, and function operators), function factories are the least used. Generally, they don’t tend to reduce overall code complexity but instead partition complexity into more easily digested chunks. Function factories are also an important building block for the very useful function operators, which you’ll learn about in Chapter “Factory fundamentals” begins the chapter with an explanation of how function factories work, pulling together ideas from scoping and environments. You’ll also see how function factories can be used to implement a memory for functions, allowing data to persist across calls. “Graphical factories” illustrates the use of function factories with examples from ggplot2. You’ll see two examples of how ggplot2 works with user supplied function factories, and one example of where ggplot2 uses a function factory internally. “Statistical factories” uses function factories to tackle three challenges from statistics: understanding the Box-Cox transform, solving maximum likelihood problems, and drawing bootstrap resamples. “Function factories + functionals” shows how you can combine function factories and functionals to rapidly generate a family of functions from data.
