Function NREVERSE. The result of NREVERSE is always EQ to the argument. NREVERSE on a VECTOR swaps pairs of elements. NREVERSE on a LIST swaps the first and the last element and reverses the list chaining between them.

Function NRECONC. The result of NRECONC is EQ to the first argument unless it is NIL, in which case the result is EQ to the second argument.