Re: Will Lua work in this situation?

[Patrick Donnelly <batrick@...>]

On Thu, May 14, 2009 at 3:29 AM, Lloyd <lloyd@cdactvm.in> wrote:
>
> Hi,
>  My application needs a continuously changing policy support. This policy
> will be implemented as Lua script. The policy will be changed only by the "C
> functions" which are called from the Lua script.As an example my initial
> policy may look like this:-
>
> if my_c_function1()==10 then
>  print("10 from my_c_function1")
> else
>  print("not 10 from my_c_function1")
> end
>
>
> Later I may need to add support for another function "my_c_function2()"
> "without recompiling my original application". So my new policy script would
> look like this:-
>
> if my_c_function1()==10 then
>  print("10")
> else
>  print("not 10")
> end
>
> if my_c_function2()==10 then
>  print("10 from my_c_function2")
> else
>  print("not 10 from my_c_function2")
> end
>
> Can I add this kind of functionality using Lua? I read the "C Libraries
> (http://www.lua.org/pil/26.2.html)" section in Lua book. Still I am not
> clear about extending without recompiling the main application code. Some
> hints would be very helpful.

This would actually be fairly simple to accomplish if you were to
compile each policy update as a separate Lua script and execute them
serially (this would not at all be slow). You could create a simple C
function that would iterate over all the scripts (policies) calling
each one. These would of course be saved in a table which you could
then add policies to.

-- 
-Patrick Donnelly

"Let all men know thee, but no man know thee thoroughly: Men freely
ford that see the shallows."

- Benjamin Franklin