experimenting

local class = {};
local class_mt = {__index = class};
local class_ref = setmetatable({}, {__mode = "k"});

function class.new(x, y)
local self = {};
  self.x = x;
  self.y = y;
  self = setmetatable(self, class_mt);
  class_ref[self] = {};
  class_ref[self].magnitude = math.sqrt(x*x + y*y);
  return self;
end

function class:getMagnitude()
  return class_ref[self].magnitude;
end

local a = class.new(1, 2, 3);
local b = class.new(-3, 7, 32/4*(-8));

print(a.x, b.y);
print(a:getMagnitude());

for _, i in next, class_ref do
  for k, v in next, _ do
    print("Round 1: ",k,"; Value: ",v);
  end
  for k, v in next, i do
    print("Round 2: ",k,"; Value: ", v);
  end
end


-- class_ref = {
-- {y = 2, x = 1} = {magnitude = math.sqrt(5)},
-- {y = 7, x = -3} = {magnitude = math.sqrt(58)}
-- }





-- both entries class_ref[a] and class_ref[b] exist
for k, v in next, class_ref do
  print(k, v);
end

b = nil;
-- note: b was the only reference to this object outside a weak table

wait(1); -- garbage collection

-- only entry class_ref[a] exists
for k, v in next, class_ref do print(k, v); end