Hi, I am a little confused about stateless iterator.

[zhuxiaohu <zxhfirefox@...>]

Hi all,

      I don't understand the different between stateless iterator and stateful iterator?  

       I know the iterator factory function return 3 values, the iter function, the invariant state, the initial value for control variable. Does the stateless iterator means that the iter function only use the invariant state and initial value for control variable to calculate the next value ? there is not any other local variable in iterator factory function (which will be the variables in closures ?

       for the exercise 7.1 in Programming in Lua, does the follow code is correct answer ?

--stateful

--[[

function fromto(n,m)

local r = m - n

return function(min, i)

if i < r then

return min + i

else

return nil

end

end,n,0

end

--]]

--stateless

local function iter(m,n)

if n + 1 < m then 

return n + 1

else 

return nil 

end

end

function fromto(n,m)

return iter, m , n-1

end

for i in fromto(1,10) do

print(i)

end

Thanks.