PPT Slide

Setf provides a facility for explicit binding ( assignment ) in Lisp.

(setf ID1 VAL1

ID2 VAL2

IDn VALn )

quotes the odd - numbered arugments ( the IDs ) and assigns the evaluation of each even - numbered argument to the preceding odd - numbered one.

( setf x 'A x A

y '( A B C ) ) y ( A B C )

( setf EL ( CAR '( A B ) ) ) EL A

Since setf performs global assignment, we will generally use it

for initializations at the top level of the Lisp interpreter.