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Understanding Variables and Data Types in Rust Programming

By the end of this lesson, you will understand Rust's syntax for declaring variables, the concept of mutability, and the various data types available in Rust. You'll also learn how to work with strings and perform basic operations.

1. Variables in Rust

In Rust, variables are declared using the let keyword. By default, variables are immutable, meaning once a value is assigned, it cannot be changed.

Declaring Variables:

let x = 5; // Immutable variable

If you need to change the value of a variable, you can declare it as mutable using the mut keyword.

Mutable Variables:

let mut y = 10; // Mutable variable
y += 5; // Now y is 15

2. Data Types in Rust

Rust is a statically typed language, meaning that all variables must have a defined type at compile time. The type can be explicitly declared, but Rust often infers the type based on the value assigned.

Common Data Types:

1. Integers:

   • Signed integers: i8, i16, i32, i64, i128, and isize (size dependent on architecture)
   • Unsigned integers: u8, u16, u32, u64, u128, and usize

   let a: i32 = 42; // Signed 32-bit integer
   let b: u64 = 100; // Unsigned 64-bit integer
   

2. Floating-point Numbers:

   • f32 (32-bit) and f64 (64-bit)

   let pi: f64 = 3.14159; // 64-bit floating point
   

3. Boolean:

   • Represents a value of either true or false.

   let is_rust_fun: bool = true;
   

4. Characters:

   • Represented by the char type, it holds a single Unicode character.

   let letter: char = 'R';
   

5. Strings:

   • Rust has two types of strings: string literals (&str) and String.
   • String literals are immutable and have a fixed size, while String is a growable, heap-allocated data structure.

   String Literals:

   let greeting: &str = "Hello, Rust!";
   

   String Type:

   let mut name = String::from("Alice");
   name.push_str(" Smith"); // Appends to the string
   

3. Type Inference

Rust’s type inference allows you to omit type annotations in many cases. The compiler will infer the type based on the assigned value.

let x = 10; // Compiler infers x as i32

However, explicit type annotations can be useful for clarity or when the type cannot be inferred.

4. Performing Basic Operations

You can perform arithmetic operations on numeric types in Rust:

let a = 5;
let b = 10;

let sum = a + b; // Addition
let difference = b - a; // Subtraction
let product = a * b; // Multiplication
let quotient = b / a; // Division
let remainder = b % a; // Modulus

For string operations, you can concatenate strings using the + operator or the format! macro:

let first_name = String::from("John");
let last_name = String::from("Doe");
let full_name = first_name + " " + &last_name; // Concatenation

let formatted_name = format!("{} {}", first_name, last_name); // Using format!

5. Conclusion

In this lesson, you learned the basics of Rust syntax, focusing on variable declarations, mutability, and data types. You explored common data types and how to perform basic operations with them. Understanding these foundational concepts is essential as you progress in your Rust programming journey.