Flash cards
Review the key moves
What is the main idea behind Rust Data Types?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___ my_num = 5; // integerPut the learning moves in the order that makes the concept easiest to apply.
Data Types
Unlike many other programming languages, variables in Rust do not need to be declared with a specified type (like "String" for text or "Int" for numbers, if you are familiar with those from C or Java ).
In Rust, the type of a variable is decided by the value you give it. Rust looks at the value and automatically chooses the right type:
Example
let my_num = 5; // integer
let my_double = 5.99; // float
let my_letter = 'D'; // character
let my_bool = true; // boolean
let my_text = "Hello"; // stringHowever, it is possible to explicitly tell Rust what type a value should be:
Example
let my_num: i32 = 5; // integer
let my_double: f64 = 5.99; // float
let my_letter: char = 'D'; // character
let my_bool: bool = true; // boolean
let my_text: &str = "Hello"; // stringYou will learn more about when you need to specify the type later in this tutorial. Either way, it is good to understand what the different types mean.
Basic data types in Rust are divided into different groups:
- Numbers - Whole numbers and decimal numbers ( i32 , f64 )
- Characters - Single letters or symbols ( char )
- Strings - Text, a sequence of characters ( &str )
- Booleans - True or false values ( bool )
Numbers
Number types are divided into two groups: integer types and floating point types.
Integer (i32)
The i32 type is used to store whole numbers, positive or negative (such as 123 or -456), without decimals:
Example
let age: i32 = 25;
println!("Age is: {}", age);Floating Point (f64)
The f64 type is used to store numbers containing one or more decimals:
Example
let price: f64 = 19.99;
println!("Price is: ${}", price);Characters (char)
The char type is used to store a single character. A char value must be surrounded by single quotes, like 'A' or 'c':
Example
let myGrade: char = 'B';
println!("{}", myGrade);Strings (&str)
The &str type is used to store a sequence of characters (text). String values must be surrounded by double quotes:
Example
let name: &str = "John";
println!("Hello, {}!", name);Booleans (bool)
The bool type can only take the values true or false :
Example
let is_logged_in: bool = true;
println!("User logged in? {}", is_logged_in);Combining Data Types
You can mix different types in the same program:
Example
let name = "John";
let age = 28;
let is_admin = false;
println!("Name: {}", name);
println!("Age: {}", age);
println!("Admin: {}", is_admin);