# Structures

There are three types of structures ("structs") that can be created using the `struct` keyword:

• Tuple structs, which are, basically, named tuples.
• The classic C structs
• Unit structs, which are field-less, are useful for generics.
``````// An attribute to hide warnings for unused code.

#[derive(Debug)]
struct Person {
name: String,
age: u8,
}

// A unit struct
struct Unit;

// A tuple struct
struct Pair(i32, f32);

// A struct with two fields
struct Point {
x: f32,
y: f32,
}

// Structs can be reused as fields of another struct
struct Rectangle {
// A rectangle can be specified by where the top left and bottom right
// corners are in space.
top_left: Point,
bottom_right: Point,
}

fn main() {
// Create struct with field init shorthand
let name = String::from("Peter");
let age = 27;
let peter = Person { name, age };

// Print debug struct
println!("{:?}", peter);

// Instantiate a `Point`
let point: Point = Point { x: 10.3, y: 0.4 };

// Access the fields of the point
println!("point coordinates: ({}, {})", point.x, point.y);

// Make a new point by using struct update syntax to use the fields of our
// other one
let bottom_right = Point { x: 5.2, ..point };

// `bottom_right.y` will be the same as `point.y` because we used that field
// from `point`
println!("second point: ({}, {})", bottom_right.x, bottom_right.y);

// Destructure the point using a `let` binding
let Point { x: left_edge, y: top_edge } = point;

let _rectangle = Rectangle {
// struct instantiation is an expression too
top_left: Point { x: left_edge, y: top_edge },
bottom_right: bottom_right,
};

// Instantiate a unit struct
let _unit = Unit;

// Instantiate a tuple struct
let pair = Pair(1, 0.1);

// Access the fields of a tuple struct
println!("pair contains {:?} and {:?}", pair.0, pair.1);

// Destructure a tuple struct
let Pair(integer, decimal) = pair;

println!("pair contains {:?} and {:?}", integer, decimal);
}``````

### Activity

1. Add a function `rect_area` which calculates the area of a `Rectangle` (try using nested destructuring).
2. Add a function `square` which takes a `Point` and a `f32` as arguments, and returns a `Rectangle` with its top left corner on the point, and a width and height corresponding to the `f32`.