copy-list
あやうく copy-list をマクロで作りかけた、、、
[1]> (setf a "a") "a" [2]> (setf ab '(a b)) (A B) [3]> (setf (car ab) a) "a" [4]> (setf ax '(a b)) (A B) [5]> (setf (car ax) a) "a" [6]> ab ("a" B) [7]> ax ("a" B) [8]> (eq (car ab) (car ax)) T [9]> (setf cab (copy-list ab)) ("a" B) [10]> (eq (car ab) (car cab)) T [11]> (setf (car ab) "a") "a" [12]> (eq (car ab) (car cab)) NIL [13]>
本体をコピーするわけではない。つまり浅いコピーってやつだ。