We have a mixin class that will allocate a subclass with its own array of handles (the handles overload * and -> so they act like pointers). If you have an instance variable you can choose to give it a different allocator, where that instance variable of object with handle `n` is the nth object in the new area. Then your instance method `barf& foo();`, instead of getting the instance variable `barf m_foo` Instead does some inlined arithmetic and gives the caller a reference to the object.