callback implementation details..

[Ando Sonenblick <ando@...>]

Gang,

I have a feeling my question here is rather, well, stupid, but lua has 
proven so amazingly flexible that I just may be surprised that what I'm 
asking isn't just stupid, but actually possible....  yet I doubt it...

Anyway, I am about to implement callbacks...   so that a script can 
call a C function to do some background process and when done, have the 
C code execute a lua call back.  Here would be a standard way:

local x, y, p1, p2;
DoSomething(x, y, {function  callback(a, b) print(a+ b) end, p1, p2});

Where DoSomething is the call to C to initiate the bg process, x and y 
are parameters for that process, and the table is the description of 
the callback:

it has the function to execute and the (variable number) of parameters 
to pass to it.

In this case, say p1 and p2 are 10 and 20 respectively, my C code 
creates a ref to the table, does the work, then using the ref calls the 
function callback, passing p1 and p2, which prints out 30.  I see no 
problems with implementing this.

What I'd love (for simplification sake) would be to somehow already 
pass the parameters to the function so that I don't have to have a 
table, or do extra parsing/passing in my C code, etc.

So, in this case, things would look like (hypothetically speaking):

local x, y, p1, p2;
DoSomething(x, y, function callback(a = p1, b = p2) print(a+ b) end);   
   -- a is preassigned to p1 and b is preassigned to p2

so in this case (assuming 10 and 20 again for p1 and p2), my C code 
could simply just call callback and the parameter a is already 10 and p 
already 20, yielding the same print out of 30.

Is anything like this possible?

thx,
ando

-----------------------
Ando Sonenblick
SpriTec Software
www.spritec.com