Please pardon the bandwidth waste on a probably OBVIOUS answer, but ...
As a first semester Lisp student, I am building a 3d tic-tac-toe array,
by using nested lists ((() ()) (() ()) ...) instead of make-array.
Creating and printing such an kludge is straightforward. What I
cannot seem to do easily is update a single entry. x(i,j,k) = new-value
It seemed that something like
(setf (first (second (first board))) new-value) ; e.g., X or O
would successfully update the (1,2,1) location. But using XLISP there
is a "bad place form" error. I guess that my method of locating the
right element does NOT actually provide anything to be bound.
I am SURE that this is trivial -- but I cannot find the way. Help!