lispdoc - results for arrayp

(arrayp object)

Function: Return true if OBJECT is an ARRAY, and NIL otherwise.

Example:

(defun maybe-set-fill-pointer (array new-length)
  "If this is an array with a fill pointer, set it to
  new-length, if that is longer than the current length."
  (if (and (arrayp array)
           (array-has-fill-pointer-p array))
      (setf (fill-pointer array)
              (max (fill-pointer array)
                   new-length))))

Mentioned in:
CLtL2 - 6.2.2. Specific Data Type Predicates
HyperSpec - Function ARRAYP