occurences.lisp

; https://codereview.stackexchange.com/questions/215682/occurrences-frequency-count-exercise-3-ch-3-in-ansi-common-lisp/215711?noredirect=1#comment417480_215711


(defun occurrences (list)
  (let ((ht (make-hash-table)))
    (let ((holder nil))
      (dolist (x list)
        (if (not (member x holder :test #'eq))
            (progn
              (push x holder)
              (setf (gethash x ht) 1))
            (setf (gethash x ht) (+ 1 (gethash x ht)))))
      (let ((holder2 nil))
        (dolist (tr holder)
          (push (cons tr (gethash tr ht)) holder2))
        (sort holder2 #'> :key #'cdr)))))