A company currently pays a fixed sum for the use of a particular licensed software package.   In determining if it has a good deal it decides to calculate its maximum use of the software from its license management log file.

Assume the software's licensing daemon faithfully records a checkout event when a copy of the software starts and a checkin event when the software finishes to its log file.

An example of checkout and checkin events are:

 License OUT @ 2008/10/03_23:51:05 for job 4974
 ...
 License IN  @ 2008/10/04_00:18:22 for job 4974



Task

Save the 10,000 line log file from    here   into a local file, then write a program to scan the file extracting both the maximum licenses that were out at any time, and the time(s) at which this occurs.

Mirror of log file available as a zip here (offsite mirror).




(defun max-licenses (&optional (logfile "mlijobs.txt"))
  (with-open-file (log logfile :direction :input)
    (do ((current-logs 0) (max-logs 0) (max-log-times '())
         (line #1=(read-line log nil nil) #1#))
        ((null line)
         (format t "~&Maximum simultaneous license use is ~w at the ~
                     following time~p: ~{~%  ~a~}."
                 max-logs (length max-log-times) (nreverse max-log-times)))
      (cl-ppcre:register-groups-bind (op time)
          ("License (\\b.*\\b)[ ]{1,2}@ (\\b.*\\b)" line)
        (cond ((string= "OUT" op) (incf current-logs))
              ((string= "IN"  op) (decf current-logs))
              (t (cerror "Ignore it." "Malformed entry ~s." line)))
        (cond ((> current-logs max-logs)
               (setf max-logs current-logs
                     max-log-times (list time)))
              ((= current-logs max-logs)
               (push time max-log-times)))))))