Lua shortest OOP

local function C(v, t) return type(v) == t and v end -- checking shortcut

local function Class(a, b) -- "a" and "b" is class_name and parent_class in any order (both optional)
  local smt, gmt = setmetatable, getmetatable
  local mt, cl = {}, {}
  mt.__index = C(a, 'table') or C(b, 'table')  -- parent class, if exists
  mt.__call = function(self, ...)
        local o = smt({}, cl)           -- new obj
        local init = cl.init or cl.new
        if not init then return o end   -- without init func - fine too
        return o, init(o, ...)          -- return obj and any returns of init func
    end
  cl.__name = C(a, 'string') or C(b, 'string') or 'class:'..tostring(cl):match("0x%x+")
  cl.__index = cl                              -- looping, but metamethod access
  cl.Super = mt.__index                        -- access to parent class with obj.Super.foo(obj)
  cl.Type = function(self, obj) return C(obj, 'table') and gmt(obj) == gmt(self) or cl.__name end
  cl.IsObjectOf = function(self, class) return rawequal(class, gmt(self)) end
  return smt(cl, mt)
end

if ... then return Class end

-- testing and examples

Foo = Class('Yo')
function Foo:init(x, y) -- same as Foo:new(x, y)
    self.x, self.y = x, y
    return 'qwe', 'rty'
end

function Foo:print()
    print(self.x, self.y)
end


fo, a, b = Foo(10, 20)

fo:print()     -- 10, 20
print(a, b)    -- qwe rty

Bar = Class(Foo, 'Yoyoyo')     -- table as parent, string as class-name
function Bar:init(x, y, w, h)
    self.Super.init(self, x, y)  -- parent class methods (overrided)
    self.w, self.h = w, h
end

function Bar:printf()
    print(self.x, self.y, self.w, self.h)
end

bar = Bar(10, 20, 30, 40)

bar:print()     -- 10 20
bar:printf()    -- 10 20 30 40
debug.debug()