closure.lua

local function list_iter (t)
   local i = 0
   local n = #t
   return function ()
      i = i + 1
      if i <= n then return t[i] end
   end
end

local t = { 10, 20, 30 }

for e in list_iter(t) do
   print(e)
end

print()

local a_iter = list_iter(t)
while true do
   local e = a_iter()
   if e == nil then
      break
   end
   print(e)
end

print()

local b_iter = list_iter(t)
for e in b_iter do
   print(e)
end

print()

-- error as 'for' expects 'c_iter' to be a factory function
local c_iter = list_iter(t)
for e in c_iter() do
   print(e)
end