Control Flow

if in Rust is an expression, not just a statement — it can produce a value, which is why you can assign the result of an if/else directly to a variable instead of declaring the variable first and assigning inside each branch.

fn main() {
    let number = 7;

    let description = if number % 2 == 0 {
        "even"
    } else {
        "odd"
    };

    println!("{} is {}", number, description);
}

7 is odd

loop, while, and for

loop runs forever until you break out of it explicitly — and break can carry a value out of the loop, becoming the loop expression's result, which while and for can't do since they're not meant to compute a value. for iterates a range or collection directly, without any manual index bookkeeping.

fn main() {
    let mut count = 0;
    let result = loop {
        count += 1;
        if count == 5 {
            break count * 2;
        }
    };
    println!("result = {}", result);

    for i in 0..3 {
        println!("i = {}", i);
    }
}

result = 10
i = 0
i = 1
i = 2

Next: vectors — Rust's growable array type.