RE: Lua Tables from 'C'

["Denis Lamarche" <brainwav@...>]

When I do a lua_tostring or lua_tonumber, do these values get poped off of 
the stack?  Cause when I pass values from lua to 'C' using functions. I 
always use index 1 to retreive the values and it always returns the correct 
one.  for example:

[LUA]
doit(21, 34, "I was here")

[C]
static int doit(lua_State *L)
{
int a, b;
char *text;

a=(int)lua_tonumber(L, 1);
b=(int)lua_tonumber(L, 2);
text=(char *)lua_tostring(L, 3);

printf("A=%d,  B=%d,  Text=%s\n", a, b, text);
//prints out:  A=21,  B=34,  Text=I was here   <------------
}

so 21 gets pushed into index #1 and 34 into #2 and "I was here" into #3.
So the top is at 3 (or -1??) and the bottom is at #1 right??
So a table would be pushed onto the stack at index #4 (after doit() is 
called).

> From: Diego Fernandes Nehab <diego@tecgraf.puc-rio.br>
> Reply-To: lua-l@tecgraf.puc-rio.br
> To: Multiple recipients of list <lua-l@tecgraf.puc-rio.br>
> Subject: RE: Lua Tables from 'C'
> Date: Mon, 15 Oct 2001 14:22:31 -0200 (BRST)
>
> > I don't understand.  Don't values get pushen onto the bottom of the 
> stack??
> > Or are tables different?  In that case wouldn't the table be at -1??  
> When I
> > call 'C' functions from lua with numbers as parameters, I can find them 
> on
> > the bottom of the stack.  This is confusing.
>
> The stack grows  up with positive numbers. New values  are pushed on the
> top!
>
> If there are 3 elements in the stack,  the bottom is at 1, the middle is
> at 2 and the top  is at 3. If you push a new elemement,  it will be at 4
> and the others will keep their indexes unchanged.
>
> You can also index elements relative  to the top, using negative numbers
> as indexes. If there  are 3 elements in the stack, the  bottom is at -3,
> the middle is at  -2 and the top is at -1. If  you push a new elemement,
> it will  be at -1  and the  other indexes will  be decreased by  one, to
> reflect their new distance to the top.
>
> So, positive indexes are absolute, negative indexes are relative to the
> top. The stack grows up, new elements at the top. That's about it.
>
> []s,
> Diego.


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