consecutive sum

.lisp

(defun consecsum (array)
  (loop :with res := (make-array 1 :adjustable t :fill-pointer 0)
        :with acc := (aref array 0)
        :for i :from 1 :below (length array)
        :for j := (- i 1)
        :if (= (aref array i) (aref array j))
          :do (incf acc (aref array i))
        :else
          :do (vector-push-extend acc res)
              (setf acc (aref array i))
        :finally (unless (= 0 acc) (vector-push-extend acc res))
                 (return res)))