Right, this came up a year ago with a version that ranks among the top here: https://news.ycombinator.com/item?id=26465857

  (defmethod performance-count ((path-file string))
    (let ((map (make-hash-table :test 'equal)))
      (with-open-file (stream path-file :direction :input :if-does-not-exist nil)
        (when stream
          (loop for line = (read-line stream nil 'end)
         until (eq line 'end)
         do
         (let ((split (split-string #\space (string-downcase line))))
           (dolist (word split)
      (let ((index (gethash word map)))
        (if index
            (setf (gethash word map) (incf index))
          (setf (gethash word map) 1))))))
          (let ((keys (sort (alexandria:hash-table-keys map) 
  (lambda(x y)(> (gethash x map)(gethash y map))))))
     (dolist (key keys)
       (format t "~A ~A~%" key (gethash key map))))))))

You don't need those extra newlines if you'd prefix every code line with two spaces, by the way. It makes it much more readable if you do that.

Nice! I didn't know that trick.

Which lisp compiler did you use?

I haven't run it, just tracked down the source because I was similarly curious about the slow runtime. If I do run it it will be with SBCL. Looking at the repo, Hoyt did as well.

That code is slow because it's working with a really long list instead of a very fast hash table