Vector: struct {
    x: float
    y: float
}

Movable: trait {
    move: fun(self, float, float)
}

implement Vector: Movable {
    move: fun(self, dx: float, dy: float) {
        self x += dx
        self y += dy
    }
}

implement Vector {
    length: fun(self) -> float {
        (self x^2 + self y^2)^0.5
    }
}

position := new Vector {
    x: 100
    y: 200
}

position move(10, 10)