stackexample.lua

local Stack = {}
Stack.__index = Stack

function Stack:push(value)
  table.insert(self,value)
end

function Stack:pop()
  return table.remove(self)
end

function Stack:new()
  local new = {}
  setmetatable(new,self)
  return new
end

local s = Stack:new()

for i = 1,10 do
  s:push(1)  -- we use : now, not .
end

local a = s:pop()
while a do
  print(a)
  a = s:pop()
end

there is a typo on line 22 it should be s:push(i)