In this chapter we’ll look at enumerations, also referred to as enums. Enums allow you to define a type by enumerating its possible values. First, we’ll define and use an enum to show how an enum can encode meaning along with data. Next, we’ll explore a particularly useful enum, called
Option, which expresses that a value can be either something or nothing. Then we’ll look at how pattern matching in the
match expression makes it easy to run different code for different values of an enum. Finally, we’ll cover how the
if let construct is another convenient and concise idiom available to you to handle enums in your code.
Enums are a feature in many languages, but their capabilities differ in each language. Rust’s enums are most similar to algebraic data types in functional languages, such as F#, OCaml, and Haskell.
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