5.6 Modifying Existing List Structure

You can modify the car and cdr contents of a cons cell with the primitives setcar and setcdr. These are 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.

• Setcar: Replacing an element in a list.
• Setcdr: Replacing part of the list backbone. This can be used to remove or add elements.
• Rearrangement: Reordering the elements in a list; combining lists.