Variables

src/variables.duck

fn main() {
    // const vars are immutable
    const x = 10;
    // let vars are mutable
    let   y = 10;

    // immutable references don't allow mutation of the thing pointed to
    const immutable_pointer_to_x = &x;
    const immutable_pointer_to_y = &y;

    // mutable references allow mutation of the thing pointed to
    const mutable_pointer_to_y = &mut y;
    // cannot take mutable references of const vars
    // const mutable_pointer_to_x = &mut x; <- error

    // f is a lambda that is allowed to make modifications to it's environment (e.g. mutating y)
    const f = mut fn() {
        // mutating const vars is still not allowed
        // x = 10; <- error
        
        // mutating y is allowed because it is a let var
        y = 20;
    };

    // f2 is a lambda that is NOT allowed to make modifications to it's environment
    const f2 = fn() {
        // even tho y is a mutable variable, f2 is not allowed to make modifications
        // y = 20; <- error
    };
    // caling f now changes y to 20
    f();
    // caling f2 won't change anything
    f2();
}