3 ms·

() is equivalent to an empty list and nil according to this notation, in which case both would be proper lists. But according to pg, in bel, (a b . c) is not a

• erik_seaberg 7y ago
  Think of a proper list like a degenerate tree with all the values on the left and structure on the right. A dotted list puts the last value on the right, where nil would usually be. Dotted lists are pretty rare. They mostly show up in association lists, where key/value pairs are stored as ((name . dave) (type . user)) and adding a pair to the front of the list shadows any other pairs with the same key.