lua_isinteger[-0, +0, –] int lua_isinteger (lua_State *L, int index); Returns 1 if the value at the given index is an integer (that is, the value is a number and is represented as an integer), and 0 otherwise.

debug.setupvalue (f, up, value) This function assigns the value value to the upvalue with index up of the function f. The function returns nil if there is no upvalue with the given index. Otherwise, it returns the name of the upvalue.

os.rename (oldname, newname) Renames the file or directory named oldname to newname. If this function fails, it returns nil, plus a string describing the error and the error code. Otherwise, it returns true.

lua_tocfunction[-0, +0, –] lua_CFunction lua_tocfunction (lua_State *L, int index); Converts a value at the given index to a C function. That value must be a C function; otherwise, returns NULL.

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_newmetatable[-0, +1, m] int luaL_newmetatable (lua_State *L, const char *tname); If the registry already has the key tname, returns 0. Otherwise, creates a new table to be used as a metatable for userdata, adds to this new table the pair __name = tname, adds to the registry the pair [tname] = new table, and returns 1. (The entry __name is used by some error-reporting functions.) In both cases pushes onto the stack the final value associated with tname in the registry.

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

3.4.6 – Concatenation The string concatenation operator in Lua is denoted by two dots ('..'). If both operands are strings or numbers, then they are converted to strings according to the rules described in §3.4.3. Otherwise, the __concat metamethod is called (see §2.4).

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

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.