debug.traceback ([thread,] [message [, level]]) If message is present but is neither a string nor nil, this function returns message without further processing. Otherwise, it returns a string with a traceback of the call stack. The optional message string is appended at the beginning of the traceback. An optional level number tells at which level to start the traceback (default is 1, the function calling traceback).

utf8.char (···)

lua_isboolean[-0, +0, –] int lua_isboolean (lua_State *L, int index); Returns 1 if the value at the given index is a boolean, and 0 otherwise.

math.sqrt (x) Returns the square root of x. (You can also use the expression x^0.5 to compute this value.)

luaL_checkstack[-0, +0, v] void luaL_checkstack (lua_State *L, int sz, const char *msg); Grows the stack size to top + sz elements, raising an error if the stack cannot grow to that size. msg is an additional text to go into the error message (or NULL for no additional text).

lua_KFunction typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx); Type for continuation functions (see §4.7).

lua_setmetatable[-1, +0, –] void lua_setmetatable (lua_State *L, int index); Pops a table from the stack and sets it as the new metatable for the value at the given index.

os.exit ([code [, close]]) Calls the ISO C function exit to terminate the host program. If code is true, the returned status is EXIT_SUCCESS; if code is false, the returned status is EXIT_FAILURE; if code is a number, the returned status is this number. The default value for code is true. If the optional second argument close is true, closes the Lua state before exiting.

luaL_argcheck[-0, +0, v] void luaL_argcheck (lua_State *L, int cond, int arg, const char *extramsg); Checks whether cond is true. If it is not, raises an error with a standard message (see luaL_argerror).

luaL_getsubtable[-0, +1, e] int luaL_getsubtable (lua_State *L, int idx, const char *fname); Ensures that the value t[fname], where t is the value at index idx, is a table, and pushes that table onto the stack. Returns true if it finds a previous table there and false if it creates a new table.