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: ldebug.h,v 2.3.1.1 2007/12/27 13:02:25 roberto Exp $
** Auxiliary functions from Debug Interface module
** See Copyright Notice in lua.h
*/
#ifndef ldebug_h
#define ldebug_h
#include "lstate.h"
#define pcRel(pc, p) (cast(int, (pc) - (p)->code) - 1)
#define getline(f,pc) (((f)->lineinfo) ? (f)->lineinfo[pc] : 0)
#define resethookcount(L) (L->hookcount = L->basehookcount)
LUAI_FUNC void luaG_typeerror (lua_State *L, const TValue *o,
const char *opname);
LUAI_FUNC void luaG_concaterror (lua_State *L, StkId p1, StkId p2);
LUAI_FUNC void luaG_aritherror (lua_State *L, const TValue *p1,
const TValue *p2);
LUAI_FUNC int luaG_ordererror (lua_State *L, const TValue *p1,
const TValue *p2);
LUAI_FUNC void luaG_runerror (lua_State *L, const char *fmt, ...);
LUAI_FUNC void luaG_errormsg (lua_State *L);
LUAI_FUNC int luaG_checkcode (const Proto *pt);
LUAI_FUNC int luaG_checkopenop (Instruction i);
#endif