Function: FOLD-STRINGS

Source

(defun fold-strings (list)
  (declare (optimize (speed 3) (safety 0) (debug 0)))
  (let ((strings '())
        (result '()))
    (dolist (object list)
      (typecase object
        (string (push object strings))
        (t (when strings
             (push (join-strings (nreverse strings)) result)
             (setf strings '()))
           (push object result))))
    (when strings
      (push (join-strings (nreverse strings)) result))
    (nreverse result)))