Mutable Reference Arrays

Part of the Fundamentals section of Coddy's Rust journey — lesson 60 of 75.

When an array is a reference you can make it mutable by using &mut. This allows you to modify the original data through the reference.
For example:

fn process_array(arr: &mut [i32]) {
	arr[0] = 3;
}

and now when you pass a mutable array into the function:

let mut numbers = [1, 2, 3, 4, 5];
process_array(&mut numbers);
// Now numbers[0] will be 3

Challenge

Easy

Call the function process_array using the provided array.

Cheat sheet

To create a mutable reference to an array, use &mut:

fn process_array(arr: &mut [i32]) {
    arr[0] = 3;
}

let mut numbers = [1, 2, 3, 4, 5];
process_array(&mut numbers);
// Now numbers[0] will be 3

Try it yourself

fn process_array(arr: &mut [i32]) {
	arr[0] = 3;
}

fn main() {
    let mut numbers = [1, 2, 3, 4, 5];
    
    // Call process_array
    
    for i in 0..numbers.len() {
        print!("{} ", numbers[i]);
    }

}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

Rust Hello World!Comments Basic Program Structure

4Operators Part 1

Arithmetic Operators Modulo Operator Arithmetic Shortcuts Comparison Operators String Comparison

7Basic IO

Printing to Console Reading User Input Recap - Till 120 Recap - True or False

10Variable Bindings

Scope Shadowing Part 1 Variable Binding Shadowing Part 2

13Arrays Continued

Mutable Reference ArraysArray Methods Recap - Product Array Recap - Reversed Array Better Print

16Final Projects

Number Pattern Pattern Finder Student Grade Calculator

2Variables Part 1

Numbers Char String Boolean Mutable Variables

5Operators Part 2

Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3

8Calculator App

Welcome Message Getting Numbers

Basic Operations

Formatted Output

11Functions

Declaring Functions Parameters and Arguments Return Values Multiple Return Values Recap - Sigma Function Recap - Validation Function

14Iterating Over Arrays

Range Guide Enhanced For Loop Borrow In Loop Common Array Operations

3Variables Part 2

Type Declaration Naming Conventions Type Inference Recap - Initialize Variables Type Casting

6Decision Making

If Expressions If-Else Match Statement Recap - If Else Nested If - Else

9Loops

For Over Series While Loop Break Continue Nested Loop Loop Labels Infinite Loop Recap - Dynamic Input

12Arrays Basics

Declaring Arrays Array as Parameter Accessing Elements Modifying Arrays Recap - Pretty Print Array

15String Operations

String Methods format! Macro String Conversion Recap - Format