Answer to Question s12
Incorrect. In the second case, the head
of the answer should be head(L) + 1. Expression
tail(L) + 1 makes no sense. Tail(L) is the address
of a ListCell (or is NULL). Say it is address a.
Tail(L) + 1 points the list cell that comes after a
in memory. There is no reason to think that the next
ListCell is anything. It might not even be owned
by your program.