Foundations of F#

CHAPTER 4Imperative Programming

As you saw in Chapter 3, you can use F# for pure functional programming. However, some issues, most notably I/O, are almost impossible to address without some kind of state change. F# does not require that you program in a stateless fashion. It allows you to use mutable identifiers whose values can change over time. F# also has other constructs that support imperative programming. You've already seen some in Chapter 3. Any example that wrote to the console included a few lines of imperative code alongside functional code. In this chapter, you'll explore these constructs, and many others, in much more detail.

First, you'll look at F#'s unit type, a special type that means "no value," which enables some aspects ...