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()}")

print('ALL TESTS PASSED')