Question

Here’s my code, I confuse the local variable ‘count’ in the return function(c1,c2) with memory strack and where does they store in?

function make_counter()
  local count = 0
  return function()
    count = count + 1
    return count
  end
end
c1 = make_counter()
c2 = make_counter()
print(c1())--print->1
print(c1())--print->2
print(c1())--print->3

print(c2())--print->1
print(c2())--print->2

Answer 1

in the return function(c1,c2) with memory strack and where does they store in?

It’s stored in the closure!

c1 is not a closure, it is the function returned by make_counter(). The closure is not explicitly declared anywhere. It is the combination of the function returned by make_counter() and the “free variables” of that function. See closures @ Wikipedia, specifically the implementation:

Closures are typically implemented with a special data structure that contains a pointer to the function code, plus a representation of the function’s lexical environment (e.g., the set of available variables and their values) at the time when the closure was created.