迭代器和泛型for

function values(t)
  local i = 0
return function () 
    i=i+1
    return t[i]
end
end
t={10,20,30}
iter=values(t)
while true do
   local val = iter()

   if not val then
     break
   else
     print(val)
   end
end
for i in values(t) do
    print(i)
end
--10
--20
--30

2.