class Vec2
  def _init(x, y)
    self.x = x
    self.y = y
  end

  def add(other)
    return Vec2(self.x + other.x,
                self.y + other.y)
  end

  ## Note that operator overloading / friend functions
  ## haven't implemented at this point (to_string won't actually
  ## override it).
  def to_string
    return "[${self.x}, ${self.y}]"
  end

end

v1 = Vec2(1, 2); assert(v1.x == 1 and v1.y == 2)
print("v1 = ${v1.to_string()}")

v2 = Vec2(3, 4); assert(v2.x == 3 and v2.y == 4)
print("v2 = ${v2.to_string()}")

v3 = v1.add(v2); assert(v3.x == 4 and v3.y == 6)
print("v3 = ${v3.to_string()}")

###############################################################################
## INHERITANCE
###############################################################################

class Shape
  def display()
    return "${self.name} shape"
  end
end

class Circle is Shape
  def _init(r)
    self.r = r
    self.name = "circle"
  end
  def area()
    return 3.14 * self.r * self.r
  end
end

class Rectangle is Shape
  def _init(w, h)
    self.w = w; self.h = h
    self.name = "rectangle"
  end
  def area()
    return self.w * self.h
  end
end

class Square is Rectangle
  def _init(w)
    ## TODO: Currently there is no way of calling super(w, h)
    ## so we're setting our self here.
    self.w = w; self.h = w
    self.name = "square"
  end
end

c = Circle(1)
assert(c.display() == "circle shape")
assert(c is Circle)
assert(c is Shape)

r = Rectangle(2, 3)
assert(r is Shape)
assert(r.area() == 6)

s = Square(4)
assert(s is Square)
assert(s is Rectangle)
assert(s is Shape)
assert(s.area() == 16)

print('ALL TESTS PASSED')