rust/src/doc/trpl/structs.md

% Structs

A struct is another form of a record type, just like a tuple. There's a difference: structs give each element that they contain a name, called a field or a member. Check it out:

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

fn main() {
    let origin = Point { x: 0, y: 0 }; // origin: Point

    println!("The origin is at ({}, {})", origin.x, origin.y);
}

There's a lot going on here, so let's break it down. We declare a struct with the struct keyword, and then with a name. By convention, structs begin with a capital letter and are also camel cased: PointInSpace, not Point_In_Space.

We can create an instance of our struct via let, as usual, but we use a key: value style syntax to set each field. The order doesn't need to be the same as in the original declaration.

Finally, because fields have names, we can access the field through dot notation: origin.x.

The values in structs are immutable by default, like other bindings in Rust. Use mut to make them mutable:

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

fn main() {
    let mut point = Point { x: 0, y: 0 };

    point.x = 5;

    println!("The point is at ({}, {})", point.x, point.y);
}

This will print The point is at (5, 0).