Variables, Mutability & Shadowing

Rust variables support two key characteristics:

• Mutability (`let mut`): To allow variable values to change, you must explicitly declare mutability using the `mut` keyword: `let mut score = 10;`.
• Variable Shadowing: You can declare a new variable with the same name as an existing variable using the `let` keyword. The new variable "shadows" the previous one, allowing you to change its value and even its data type while keeping the variable name.

Let's run a program exploring mutability controls and variable shadowing:

fn main() {
    // Immutable variable
    let x = 5;
    println!("x: {}", x);

    // Mutable variable
    let mut y = 10;
    y = 15;
    println!("y: {}", y);

    // Shadowing: redeclaring with 'let'
    let spaces = "   "; // String type
    let spaces = spaces.len(); // Shadowed variable is now an integer type
    println!("Spaces length: {}", spaces);
}