Rust Data Types
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"; // string
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However, 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"; // string
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You 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,u32,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.
Integers (i32 and u32)
Integer types are used to store whole numbers without decimals.
Two common integer types are i32 and u32:
i32can store positive and negative whole numbersu32can only store zero or positive whole numbers
Example
let temperature: i32 = -5;
let age: u32 = 25;
println!("Temperature: {}", temperature);
println!("Age: {}", age);
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The u in u32 means unsigned, which means the value cannot be negative. This makes u32 useful for values such as age, counts, and sizes.
Floating Point (f64)
The f64 type is used to store numbers containing one or more decimals:
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':
Strings (&str)
The &str type is used to store a sequence of characters (text). String values must be surrounded by double quotes:
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);
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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);
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