Re: I miss table.foreach

[Sven Olsen <sven2718@...>]

API functions like lua_getfield() respect proxies, so why not lua_next() as well?  

Hrm.  Maybe putting the table iteration hook in __pairs, rather than __next, is the better choice.

If lua_next() respected an iteration metamethod, then most C table iterations would pick up an extra O(n) overhead cost.  

And __pairs also gives you the power to use a state variable other than the table itself, which can be handy.

I'd still like to have a version of next() available in Lua that respects proxy tables -- though that's easy enough to get:

  function next(t,k)

    local f,s = pairs(t)

    return f(s,k)

  end

One can use a similar trick at the API level to make a version of lua_next() that respects the __pairs metamethod -- but, there's enough extra overhead in each call that you probably want to be careful about just where you use it.

-Sven

int lua_nextmeta (lua_State *L, int i) {

  int oldtop=lua_gettop(L);

  if (!luaL_getmetafield(L,i, "__pairs")) {

    return lua_next(L,i);

  }

  if(i<0) {

    i=lua_gettop(L)+i;

  }

  lua_checkstack(L,2);

  lua_pushvalue(L,i); // ...,k,__pairs, t

  lua_call(L,1,2); // ...,k,iterfun,s

  lua_pushvalue(L,oldtop); // ...,k,iterfun,s,k

  lua_remove(L,oldtop); //...,iterfun,s,k

  lua_call(L,2,2); // ..., k2, v2

  if(lua_isnil(L,-2)) {

    lua_pop(L,2);

    return 0;

  }

  return 1;

}