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: lualib.h,v 1.36.1.1 2007/12/27 13:02:25 roberto Exp $
** Lua standard libraries
** See Copyright Notice in lua.h
*/
#ifndef lualib_h
#define lualib_h
#include "lua.h"
/* Key to file-handle type */
#define LUA_FILEHANDLE "FILE*"
#define LUA_COLIBNAME "coroutine"
LUALIB_API int (luaopen_base) (lua_State *L);
#define LUA_TABLIBNAME "table"
LUALIB_API int (luaopen_table) (lua_State *L);
#define LUA_IOLIBNAME "io"
LUALIB_API int (luaopen_io) (lua_State *L);
#define LUA_OSLIBNAME "os"
LUALIB_API int (luaopen_os) (lua_State *L);
#define LUA_STRLIBNAME "string"
LUALIB_API int (luaopen_string) (lua_State *L);
#define LUA_MATHLIBNAME "math"
LUALIB_API int (luaopen_math) (lua_State *L);
#define LUA_DBLIBNAME "debug"
LUALIB_API int (luaopen_debug) (lua_State *L);
#define LUA_LOADLIBNAME "package"
LUALIB_API int (luaopen_package) (lua_State *L);
/* open all previous libraries */
LUALIB_API void (luaL_openlibs) (lua_State *L);
#ifndef lua_assert
#define lua_assert(x) ((void)0)
#endif
#endif