fill-pointer vector → fill-pointer

(setf (fill-pointer vector) new-fill-pointer)

vector — a vector with a fill pointer.

fill-pointer, new-fill-pointer — a valid fill pointer for the vector.

Accesses the fill pointer of vector.

(setq a (make-array 8 :fill-pointer 4)) → #(NIL NIL NIL NIL) 
(fill-pointer a) → 4 
(dotimes (i (length a)) (setf (aref a i) (* i i))) → NIL 
a → #(0 1 4 9) 
(setf (fill-pointer a) 3) → 3 
(fill-pointer a) → 3 
a → #(0 1 4) 
(setf (fill-pointer a) 8) → 8 
a → #(0 1 4 9 NIL NIL NIL NIL)

Should signal an error of type type-error if vector is not a vector with a fill pointer.

make-array, length

There is no operator that will remove a vector’s fill pointer.