syntax: paren

(class Rectangle
    (method init (self a b)
        (update self.a a)
        (update self.b b))

    (method area (self)
        (* self.a self.b)))

(class Circle
    (method init (self r)
        (update self.r r))

    (method area (self)
        (* 3.14 (* self.r self.r))))

(class Object
    (method start (self)
        (define e (! Rectangle.new 2 4))
        (define f (! e.area ))
        (! f.display )
        (define c (! Circle.new 4))
    (define g (! c.area ))
        (! g.display )))