If I have a function that creates a function.

createafunc()
  local newfunc = function()
    -- do lots of stuff
  end

  return newfunc
end

Does the newfunc's code get recreated everytime internally when I call createfunc? Or is there only a simply variable assignment that happens behind the scenes when createafunc is called? (ie, the internal function is already defined when the file was executed, so newfunc is simply assigned to point to that location) Basically what I want to know, is if there is going to be a big overhead every time I call createafunc if the newfunc in it is huge. So im wondering if the internal operations is newfunc = [function at this address] return newfunc or newfunc = function that does this, this, then this and so on (as the functoin is defined) return newfunc I hope its understandable what I mean :).

I put these functions in:

function testmem(func)  collectgarbage(0)  local store = {}  local mem1 = gcinfo()  for i = 1, 10000 do    table.insert(store, func())  end  local mem2 = gcinfo()  print(mem2 - mem1)endfunction f1()  local newfunc = function()  end  return newfuncendfunction f2()  local newfunc = 1.0  return newfuncendfunction f3()  local newfunc = function()  	local t = {}  	table.insert(t, 1)  	local text  	for a = 1, 200 do  	  text = text .. tostring(a) .. " "  	end  end  return newfuncend

The first function fills a table with 10000 copies of the result of a function and prints the difference in memory use before and after.

f1 returns a function.
f2 returns a number.
f3 returns a more complex function than f1.

Then in the Lua interpreter I did:

> dofile("func.lua")> testmem(f1)607> testmem(f2)256> testmem(f3)607

The size of the function (f1 compared to f3) doesn't seem to make a difference so it looks like it's created once and referenced multiple times.

This analysis may be wrong, if so could someone point out the error or errors in my reasoning please.

Fulby

Thanks, I think your reasoning is correct.

Whats interesting though, is how both functions take up the same about of space in dynamic memory. Obviously the bytecode for a function is not stored in dynamic memory then?

Edit: thinking about it, it makes sense. Its just like in any other programming language. But in lua, there are only function pointers, since all functions can be re-assigned. These function pointers are stored in dynamic memory.

If I remember the explanation in the Lua book right, each function is just a block of code...you're not recreating the function each time, but you ARE creating "closures" each time. Any variables that are local to that particular instance of the function are stored somewhere else.