string.reverse (s)s

math.log (x [, base]) Returns the logarithm of x in the given base. The default for base is e (so that the function returns the natural logarithm of x).

luaL_addchar[-?, +?, m] void luaL_addchar (luaL_Buffer *B, char c); Adds the byte c to the buffer B (see luaL_Buffer).

luaL_setmetatable[-0, +0, –] void luaL_setmetatable (lua_State *L, const char *tname); Sets the metatable of the object at the top of the stack as the metatable associated with name tname in the registry (see luaL_newmetatable).

io.close ([file]) Equivalent to file:close(). Without a file, closes the default output file.

luaL_checkoption[-0, +0, v] int luaL_checkoption (lua_State *L, int arg, const char *def, const char *const lst[]); Checks whether the function argument arg is a string and searches for this string in the array lst (which must be NULL-terminated). Returns the index in the array where the string was found. Raises an error if the argument is not a string or if the string cannot be found. If def is not NULL, the function uses d

package.loaded A table used by require to control which modules are already loaded. When you require a module modname and package.loaded[modname] is not false, require simply returns the value stored there. This variable is only a reference to the real table; assignments to this variable do not change the table used by require.

lua_geti[-0, +1, e] int lua_geti (lua_State *L, int index, lua_Integer i); Pushes onto the stack the value t[i], where t is the value at the given index. As in Lua, this function may trigger a metamethod for the "index" event (see §2.4). Returns the type of the pushed value.

lua_copy[-0, +0, –] void lua_copy (lua_State *L, int fromidx, int toidx); Copies the element at index fromidx into the valid index toidx, replacing the value at that position. Values at other positions are not affected.

math.ceil (x) Returns the smallest integral value larger than or equal to x.