Accessing Elements

Part of the Fundamentals section of Coddy's Rust journey — lesson 57 of 75.

Each value in an array is called an element, and each element has an index. The indices start from 0 to the length of the array minus one. For example take a look at the next array:

let letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];

Element a is at index 0
Element b is at index 1
...
Element g is at index 6

To access an element of an array, we can use its index within square brackets. For example, to access the first element of an array named letters, we would use letters[0].

Here's an example:

let numbers = [10, 20, 30, 40, 50];
let element = numbers[2];

The variable element will hold the value 30 because it accesses the third element (which has an index of 2).

Challenge

Easy

Create a function named values that receives an array as an argument and prints all of the items in the array one after the other.

To iterate over an array use the .len() field:

for i in 0..numbers.len() {
    // code
}

This way i will iterate from 0 to numbers.len() (not including) which is exactly all of the array indices.

Cheat sheet

Array elements are accessed using indices starting from 0:

let letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
let first_element = letters[0]; // 'a'
let third_element = letters[2]; // 'c'

To iterate over an array, use .len() to get the array length:

for i in 0..numbers.len() {
    // i goes from 0 to numbers.len() (exclusive)
}

Try it yourself

fn values(arr: &[i32]) {
    // Write code here
}

fn main() {
    let numbers = [10, 20, 30, 40, 50];
    values(&numbers);
}

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 Arrays Array 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 ParameterAccessing ElementsModifying Arrays Recap - Pretty Print Array

15String Operations

String Methods format! Macro String Conversion Recap - Format