📦 mutable variable — Mutability in Rust

as i mentioned, variables are immutable by default. This means that once a value is assigned to a variable, it cannot be changed. However, sometimes you may need to modify a variable's value during execution. In such cases, you can declare the variable as mutable by using the mut keyword.

Declaring Mutable Variables

To declare a mutable variable in Rust, simply add mut before the variable name.

Example: Mutable Variables

fn main() {
    let mut x = 5; // mutable variable
    println!("x is: {}", x); // Output: x is: 5
    x = 10; // changing the value of x
    println!("Now, x is: {}", x); // Output: Now, x is: 10
}

🔎 Line-by-line breakdown:

• let mut x = 5; — This declares a mutable variable x and assigns it the value 5.

• x = 10; — This changes the value of x from 5 to 10.

Why Use Mutability?

• Memory Safety: By default, Rust prevents accidental changes to variables, which helps avoid bugs and ensures that the program’s state is predictable.

• Explicit Intent: Declaring variables as mut makes it clear in the code that the variable is intended to be modified. This improves code readability and reduces confusion.

Example: without Mutability

fn main() {
    let x = 5; // immutable variable
    println!("x is: {}", x); // Output: x is: 5
    // x = 10; // This would cause an error: cannot assign twice to immutable variable
}

💡 Key points to remember:

• In Rust, variables are immutable by default.

• Use the mut keyword to make a variable mutable if you plan to change its value after initial assignment.

• You cannot change the value of an immutable variable.