Re: Table lookups versus String matching

[Luis F Urrea <lfurrea@...>]

Wim,

1,2) I don't think it would really make a difference judging by the size of the table, so as Sam pointed out, probably elegance and readability should prevail

3) I tried your suggestion but it seems i am doing something wrong since it tells me that I am attempting to call a string value.

Sam, 

The overhead of the linear grow needs to be considered since all actions will be exectuted through the state machine. Thank you for pointing that out

The third suggestion looks a little bit cryptical but we're testing right now

On Wed, Feb 25, 2009 at 1:57 PM, Sam Roberts <vieuxtech@gmail.com> wrote:

On Wed, Feb 25, 2009 at 11:38 AM, Luis F Urrea <lfurrea@gmail.com> wrote:
> Our team is learning the subtleties of LUA and we are on a small newbies
> debate.
>
> We are wondering what would be cheaper between calling a function from a
> table lookup or a string matching function.

"cheaper" as in "faster"?

Benchmark it! If you can't tell the difference in the bm, then make it
as readable as possible.

> Basically we have a Table that stores the name of the function. When a state
> machine runs and returns the name of the function we have the option to do
> this:

The overhead of an
 if a == "this" then
 elseif b == "that"
 elseif ..

is linear in the number of conditions, so will get worse and worse as
you add conditions.

The overhead of a table lookup "might" be higher than a single
comparison, but should increase much less than linearly as the table
size grows.

> local actions = { pAuthRequest =  function ()
>                                          print("Auth request coming!")
>                                       end,
>                       ClientSend =  function ()
>                                        master:send(auth_string)
>                                     end,
>                       pCommandReply =  function ()
>                                           print("Woohooo")
>                                        end,
>                       pWaiting = function ()
>                                     print("Waiting for more")
>                                  end,
>                    }
>
> local action = ""> >          action()

Or

({
  a = ...,
  b = ...,
})[a.action]()

Sam