5.6 Modifying Existing List Structure

You can modify the CAR and CDR contents of a cons cell with the primitives setcar and setcdr. We call these "destructive" operations because they change existing list structure.

Common Lisp note: Common Lisp uses functions rplaca and rplacd to alter list structure; they change structure the same way as setcar and setcdr, but the Common Lisp functions return the cons cell while setcar and setcdr return the new CAR or CDR.

5.6.1 Altering List Elements with setcar		Replacing an element in a list.
5.6.2 Altering the CDR of a List		Replacing part of the list backbone. This can be used to remove or add elements.
5.6.3 Functions that Rearrange Lists		Reordering the elements in a list; combining lists.