Tuple Structs

If the field names are unimportant, you can use a tuple struct:

struct Point(i32, i32);

fn main() {
    let p = Point(17, 23);
    println!("({}, {})", p.0, p.1);

This is often used for single-field wrappers (called newtypes):

struct PoundsOfForce(f64);
struct Newtons(f64);

fn compute_thruster_force() -> PoundsOfForce {
    todo!("Ask a rocket scientist at NASA")

fn set_thruster_force(force: Newtons) {
    // ...

fn main() {
    let force = compute_thruster_force();
  • Newtypes are a great way to encode additional information about the value in a primitive type, for example:
    • The number is measured in some units: Newtons in the example above.
    • The value passed some validation when it was created, so you no longer have to validate it again at every use: ’PhoneNumber(String)orOddNumber(u32)`.
  • Demonstrate how to add a f64 value to a Newtons type by accessing the single field in the newtype.
    • Rust generally doesn’t like inexplicit things, like automatic unwrapping or for instance using booleans as integers.
    • Operator overloading is discussed on Day 3 (generics).
  • The example is a subtle reference to the Mars Climate Orbiter failure.