Lesson 04 of 20

6 mins read

Scalar & Compound Types (Integers, Floats, Tuples, Arrays)

In Plain English

Rust is statically typed with strong type inference. It features scalar types (integers i8-i128, u8-u128, isize/usize, f32/f64, bool, char) and compound types (tuples and fixed-size arrays [T; N]).

The Mental Model

"Scalar types are individual Lego bricks (single numbers or letters). Compound types are assembled Lego kits—a tuple is a multi-color assorted kit, and an array is a rigid tray of identical bricks."

Deep Dive: How It Works

Integer Types: i32 is the default integer type. usize matches the target CPU pointer architecture.

Tuples: Group multiple values of different types with fixed arity: let t: (i32, f64, &str) = (1, 2.5, "hi");.

Arrays: Fixed-length lists stored contiguously on the stack: let a: [i32; 3] = [10, 20, 30];.

Syntax Blueprint

let tuple: (i32, bool) = (42, true); let arr: [i32; 3] = [1, 2, 3];

Tuples access elements with .index (tuple.0), while arrays access with [index] (arr[0]).

Core Rules to Remember

Type Annotation: let x: i64 = 5000; explicitly defines variable size.

Tuple Indexing: tuple.0 and tuple.1 extract heterogeneous fields.

Array Sizing: Arrays have fixed sizes known at compile time ([type; count]).

Common Beginner Traps & How to Fix Them

Mistake:Trying to change the length of a Rust array.

Why it happens: Standard Rust arrays [T; N] have a fixed size on the stack and cannot grow.

How to fix: If you need a growable dynamically-sized collection, use Vec<T> instead.

Pro Tip: Use numeric literal underscores for readability: let one_million = 1_000_000_u32;.

Live Interactive Example

Hit Run Code to see it live

Scalars, Tuples and Arrays

Rust 1.78 / rustc

Output Console

Click "Run Code" to view the rendered output.

How it works: Demonstrates primitive types, tuple field access, and array indexing.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Extract tuple and array elements

Declare let config: (&str, u16) = ("localhost", 8080);
Declare let ports: [u16; 2] = [8080, 8443];
Print "Server: localhost on port 8080 | SSL: 8443".

Sandbox Output

Click "Run & Check" to test your solution.

Finished reading and practicing?

Mark this lesson as completed to update your course progress.