Re: [ANN] Lua 5.2.0 (alpha) now available

[Petite Abeille <petite_abeille@...>]

On Dec 13, 2010, at 4:05 AM, Javier Guerra Giraldez wrote:

> next() does a linear scan of the array part before starting with the
> hash part.  if you have a big but empty array part it can take a
> significant time.

Hmmm... damn, you are right! :)

In ltable.luaH_next, that first loop probes the array part sequentially until it find a non-nil value... oh, well...

int luaH_next (lua_State *L, Table *t, StkId key) {
  int i = findindex(L, t, key);  /* find original element */
  for (i++; i < t->sizearray; i++) {  /* try first array part */
    if (!ttisnil(&t->array[i])) {  /* a non-nil value? */
      setnvalue(key, cast_num(i+1));
      setobj2s(L, key+1, &t->array[i]);
      return 1;
    }
  }
  for (i -= t->sizearray; i < sizenode(t); i++) {  /* then hash part */
    if (!ttisnil(gval(gnode(t, i)))) {  /* a non-nil value? */
      setobj2s(L, key, gkey(gnode(t, i)));
      setobj2s(L, key+1, gval(gnode(t, i)));
      return 1;
    }
  }
  return 0;  /* no more elements */
}