Re: nested __index

["temp 213 qwe" <temp213@...>]

It is a more general question why in this __indexing chain 
when finally found __index metamethod is a function, it is 
called with last table in chain as argument, but not the first 
one who actually triggered indexing.

Yes, i could store a link to initial table somewhere, and then 
track back who actually triggered initial indexing, but this 
would require "parent" table be aware of inherited "children".


lvm.c:

void luaV_finishget (lua_State *L, const TValue *t, TValue 
*key, StkId val, const TValue *slot) {
  int loop;  /* counter to avoid infinite loops */
  const TValue *tm;  /* metamethod */
  const TValue *t0 = t;
...
//      luaT_callTMres(L, tm, t, key, val);  /* call it */
      luaT_callTMres(L, tm, t0, key, val);  /* call it */




On Fri, 25 Aug 2023 21:51:56 -0400
 David Favro <lua@meta-dynamic.com> wrote:
> On August 25, 2023 12:58:40 PM EDT, temp 213 qwe 
> <temp213@gorodok.net> wrote:
>
> > "child" table could store a link to "parent" (in __index 
> > actually), but
> > if at 
> > the end of nested __indexing process we got last "parent" as 
> > self,
> > there is no 
> > way to get a child who actually triggered it, or?
>
> If I understand correctly what you are asking, this is a 
> common request.
>
> You have two options, either use functions for __index all 
> the way down and choose a technique to carry a reference to 
> the original table into successive calls, or modify the Lua 
> runtime to pass in the originating table to the final __index 
> function as a third parameter.
>
> I use a personal fork of Lua with this modification amongst 
> others, and I imagine that I am not the only one.
>
> See for instance: 
> http://lua-users.org/lists/lua-l/2016-02/msg00287.html
>
> -- David