if expressions

You use if very similarly to how you would in other languages:

fn main() {
    let mut x = 10;
    if x % 2 == 0 {
        x = x / 2;
    } else {
        x = 3 * x + 1;
    }
}

In addition, you can use it as an expression. This does the same as above:

fn main() {
    let mut x = 10;
    x = if x % 2 == 0 {
        x / 2
    } else {
        3 * x + 1
    };
}

Because if is an expression and must have a particular type, both of its branch blocks must have the same type. Consider showing what happens if you add ; after x / 2 in the second example.