Rust for C-Programmers

2.3 Variables and Mutability

2.3.1 Immutable by Default

In Rust, variables are immutable by default, enhancing safety by preventing unintended changes.

Rust Example:

fn main() {
    let x = 5;
    // x = 6; // Error: cannot assign twice to immutable variable
}

To make a variable mutable, use the mut keyword.

fn main() {
    let mut x = 5;
    x = 6; // Allowed
    println!("The value of x is: {}", x);
}

2.3.2 Comparison with C

In C, variables are mutable by default.

int x = 5;
x = 6; // Allowed

To make a variable constant in C, you use the const keyword.

const int x = 5;
// x = 6; // Error: assignment of read-only variable ‘x’