21.2 Overview of Patterns

Rust’s patterns are versatile and take many shapes:

  • Literal Patterns: Match exact values (e.g., 42, true, or "hello").
  • Identifier Patterns: Match anything, binding the matched value to a variable (e.g., x).
  • Struct Patterns: Destructure structs, such as Point { x, y }.
  • Enum Patterns: Match specific variants, like Some(x) or Color::Red.
  • Tuple Patterns: Unpack tuples into their constituent parts, e.g., (left, right).
  • Slice & Array Patterns: Match array or slice contents, for example [first, rest @ ..].
  • Reference Patterns: Match references, optionally binding the dereferenced value.
  • Wildcard Patterns (_): Ignore any value you don’t need to name explicitly.

Patterns show up in:

  1. match Expressions (the most powerful form of branching).
  2. if let, while let, and let else (convenient one-pattern checks).
  3. let Bindings (destructuring data when declaring variables).
  4. Function and Closure Parameters (unpack arguments right in the parameter list).