decf
(decf place [delta])
Decrements the number stored in place by delta (default 1), stores the result back into place, and returns the new value. place may be any location setf accepts. It expands into (setf place (- place delta)).
(decf place [delta])
Decrements the number stored in place by delta (default 1), stores the result back into place, and returns the new value. place may be any location setf accepts. It expands into (setf place (- place delta)).