3 ms·

append concatenates lists so you'd need (append nil '(foo))

• DonaldFisk 4y ago
  It actually leaves both its arguments unaltered and creates a new list. There's another function called nconc which does concatenate them, changing its first argument to the new list (unless its first argument is NIL).
  • aidenn0 4y ago
    Note that append does not copy the last argument, so there is structure sharing when you use it.