Module 1Variables & TypesLesson 6 of 1020 min

Tuples & Arrays Intro

Fixed-size groups of values: quote pairs, OHLC bars, and small matrices of numbers.

Tuples — heterogeneous, fixed length

rust

let quote: (f64, f64) = (100.0, 100.05); // bid, ask
let (bid, ask) = quote; // destructure
let mid = (quote.0 + quote.1) / 2.0;

Great for returning multiple values without a full struct yet.

Arrays — homogeneous, fixed length

rust

fn main() {
    let closes: [f64; 5] = [10.0, 10.5, 10.25, 10.75, 11.0];
    println!("first={} last={}", closes[0], closes[4]);
    println!("len={}", closes.len());
}

Output

first=10 last=11
len=5

Arrays live on the stack (when small) and have size known at compile time.

When to use which

Need	Prefer
bid+ask pair quickly	tuple or later `struct Quote`
5 known scenario shocks	array `[f64; 5]`
Growing trade list	`Vec` (Module 4)

Example: OHLC

rust

fn main() {
    let bar: (f64, f64, f64, f64) = (100.0, 102.0, 99.5, 101.0);
    let (o, h, l, c) = bar;
    println!("range = {:.2}", h - l);
    println!("ret   = {:.4}", c / o - 1.0);
}

Output

range = 2.50
ret   = 0.0100

Exercise

Store 4 closes in an array; print first/last and a simple return.

Challenge

Make an array of 3 (bid, ask) tuples and print the mid for each.

Tips

Array type is [T; N] — length is part of the type
Out-of-bounds index panics at runtime
Destructuring makes tuple code readable

Try it live

Tuples & Arrays IntroRust 2021

Loading editor…

Output

Press Run to compile and execute.