Lua返回一个Closures函数实例

 function add_to_display(digit)
  print("Call add_to_display");
  print(digit);
 end

 function digitButton(digit)
  return Button{//return a table and the function(Button), it means that the Button receives the param(the table{...})
      label = tostring(digit),
      action = function()
         print("digit: ", digit);
         add_to_display(digit);
         end
       }

 end

 local fun = digitButton(3);

end

 function values(t)
  local i = 0;
  return function()
     i = i + 1;
     return t[i];
    end
 end

 iter = values(t_);

 while true do
  local element = iter();
  if element == nil then
   break;
  end

  print(element);
 end

end