Pattern matching

Pattern matching is a programming construct in which we can match a given expression or value against a pattern. This can be used to implement control flow logic in a more expressive and concise way than it is possible with traditional conditional statements. Pattern matching is a common feature in Functional languages such as Haskell, OCaml and Elixir.

In Rust, pattern matching can be used in a variety of ways, from let and match expressions for flow control to function parameters as a way to destructure complex data. Like in OCaml, Rust’s match expressions are exhaustive, meaning they must handle all possible cases for a given matched expression.

When combined with Algebraic data types, pattern matching can become a very powerful and elegant tool to describe control flow and computation in general.

use std::f32::consts::PI;
 
enum Shape {
    Rectangle { width: u32, height: u32 },
    Circle { radius: u32 },
}
 
impl Shape {
    fn area(&self) -> f32 {
        match self {
            Shape::Circle { radius } => PI * (radius.pow(2) as f32),
            Shape::Rectangle { width, height } => (width * height) as f32,
        }
    }
}