Revert prior attempted optimisation. Gridding the land pays in some situations, but not all. Restricting to an upper bound might help, but overall, seems too fuzzy to be worth it. On one side is increased cost of Add/Delete + extra test on collision check, on the other is skipping the list iteration. Perhaps for large lists.
/*
** $Id: ltable.h,v 2.10.1.1 2007/12/27 13:02:25 roberto Exp $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/
#ifndef ltable_h
#define ltable_h
#include "lobject.h"
#define gnode(t,i) (&(t)->node[i])
#define gkey(n) (&(n)->i_key.nk)
#define gval(n) (&(n)->i_val)
#define gnext(n) ((n)->i_key.nk.next)
#define key2tval(n) (&(n)->i_key.tvk)
LUAI_FUNC const TValue *luaH_getnum (Table *t, int key);
LUAI_FUNC TValue *luaH_setnum (lua_State *L, Table *t, int key);
LUAI_FUNC const TValue *luaH_getstr (Table *t, TString *key);
LUAI_FUNC TValue *luaH_setstr (lua_State *L, Table *t, TString *key);
LUAI_FUNC const TValue *luaH_get (Table *t, const TValue *key);
LUAI_FUNC TValue *luaH_set (lua_State *L, Table *t, const TValue *key);
LUAI_FUNC Table *luaH_new (lua_State *L, int narray, int lnhash);
LUAI_FUNC void luaH_resizearray (lua_State *L, Table *t, int nasize);
LUAI_FUNC void luaH_free (lua_State *L, Table *t);
LUAI_FUNC int luaH_next (lua_State *L, Table *t, StkId key);
LUAI_FUNC int luaH_getn (Table *t);
#if defined(LUA_DEBUG)
LUAI_FUNC Node *luaH_mainposition (const Table *t, const TValue *key);
LUAI_FUNC int luaH_isdummy (Node *n);
#endif
#endif