Struct and type alias - Polygon

---

• The simplest way to represent a polygon (a series of points) is a vector of Point instances.
• We can even give it a name using the type keyword.
• Despite its name it does not create a new type, just an alias.
• That's why we cannot use impl to add a method.

examples/struct/polygon-type/src/main.rs

struct Point {
    x: i32,
    y: i32,
}

type Polygon = Vec<Point>;

// cannot define inherent `impl` for a type outside of the crate where the type is defined
// impl Polygon {
//     fn length(&self) {
//     }
// }

fn main() {
    let poly: Polygon = vec![
        Point {x: 3, y: 7},
        Point {x: 10, y: 6},
        Point {x: 23, y: 12},
        Point {x: -2, y: -2},
    ];

    for point in poly {
        println!("x: {} y: {}", point.x, point.y)
    }
}

x: 3 y: 7
x: 10 y: 6
x: 23 y: 12
x: -2 y: -2