Re: Closures & Recursion

[David Jones <drj@...>]

On 28 Jul 2006, at 13:24, Stefan Brantschen wrote:

> Newbie question: I ran into the question how to use closures with  
> recursion -- consider this snippet:
>
> local function visited (x)
> -- Check and register if a table 'x' has been visited
>   local vis = {}
>   return function (x)
>   for _, v in pairs(vis) do
>     if x == v then return true
>   end
>   v[#v+1] = x
>   return false
> end


Other people have answered your closure problem I believe.  I have a  
data structure improvement.

using vis as a characteristic table is way more efficient, simply  
associate "true" with each visited value:

if vis[x] then return true end
vis[x] = true
return false

I hope I'm not barking up the wrong tree here.

drj