[Rust Guide] 3.3. Data Types - Compound Types

3.3.0. Before the Main Text

Welcome to Chapter 3 of your Rust self-study. There are 6 sections in total:

• Variables and Mutability
• Data Types: Scalar Types
• Data Types: Compound Types (this article)
• Functions and Comments
• Control Flow: if else
• Control Flow: Loops

Through the mini-game in Chapter 2 (strongly recommended for beginners who haven't read it), you should already have learned basic Rust syntax. In Chapter 3, we will go deeper into general programming concepts in Rust.

3.3.1. Introduction to Compound Types

• Compound types group multiple values into one type
• Rust provides: Tuple and Array

3.3.1. Tuple

Characteristics:

• Can hold multiple values of different types
• Fixed length

fn main(){
    let tup:(u32,f32,i64) = (6657, 0.0721, 114514);
    println!("{},{},{}",tup.0,tup.1,tup.2);
    // Output: 6657,0.0721,114514
}

Destructuring:

fn main(){
    let tup:(u32,f32,i64) = (6657, 0.0721, 114514);
    let (x, y, z) = tup;
    println!("{},{},{}", x, y, z);
}

Access:

println!("{},{},{}", tup.0, tup.1, tup.2);

3.3.2. Array

Characteristics:

• Same type elements
• Fixed length

let a = [1, 1, 4, 5, 1, 4];

Use cases:

• Stack allocation
• Fixed size needed
• Less flexible than Vec

Type:

let machine: [u32;4] = [6, 6, 5, 7];

Initialization:

let a = [3;2];
let b = [3, 3, 3];

Access:

let machine = [6, 6, 5, 7];
let wjq = machine[0];

Out-of-bounds:

• Compile-time or runtime error
• Rust enforces bounds checking

Memory model:

• Continuous memory layout

Comparison:

Feature	C	C++	Rust
Memory model	Continuous	Continuous	Continuous
Safety	No bounds check	std::array has checks, raw arrays do not	Enforced bounds check
Dynamic array	Manual memory	std::vector	Vec
Multi-dimensional	Yes	Yes	Yes
Special features	Simple	Rich STL	Ownership & borrowing

Example:

let a = 5;
let machine = [6, 6, 5, 7];
let wjq = machine[a];

let a = [1, 9, 10, 4, 5];
let machine = [6, 6, 5, 7];
let wjq = machine[a[4]];