Bastien <bzg@altern.org> writes:

> Hi Martin,
>
> Martin Halder <martin.halder@gmail.com> writes:
>
>> this is fantastic, already love lisp, thanks a lot.. now I have exactly
>> what I wanted.. additionally I needed the time format in industrial mode
>> (1h = 100m = 100s), implemented in ihms.
>
> thanks for these functions -- I allowed myself to add them to
> Worg/org-hacks.html, in a new "Times computation" section:
>
>   http://orgmode.org/worg/org-hacks.html
>
> I added these functions I myself wrote for a particular purpose:
>
> #+begin_src emacs-lisp
> (defun org-hh:mm:ss-string-to-seconds (s)
>   "Convert a string HH:MM:SS to a number of seconds."
>   (when (string-match "\\([0-9]+\\):\\([0-9]+\\):\\([0-9]+\\)" s)
>     (let ((hour (string-to-number (match-string 1 s)))
> 	  (min (string-to-number (match-string 2 s)))
> 	  (sec (string-to-number (match-string 3 s))))
>       (+ (* hour 3600) (* min 60) sec))))
>
> (defun org-subtract-hh:mm:ss-time (t1 t2)
>   "Substract two hh:mm:ss time values."
>   (let* ((sec (- (org-hh:mm:ss-string-to-seconds t2)
> 		 (org-hh:mm:ss-string-to-seconds t1)))
> 	 (hour (floor (/ sec 3600)))
> 	 (min (floor (/ (- sec (* 3600 hour)) 60)))
> 	 (secs (round (- sec (* 3600 hour) (* 60 min)))))
>     (format "%.2d:%.2d:%.2d" hour min secs)))
> #+end_src
>
> With these function, you can subtract durations in a table like this:
>
> | Part  |    Begin |      End | Duration |
> |-------+----------+----------+----------|
> | One   | 00:00:00 | 00:01:11 | 00:01:11 |
> | Two   | 00:01:12 | 00:02:00 | 00:00:48 |
> | Three | 00:02:05 | 00:16:06 | 00:14:01 |
> #+TBLFM: $4='(org-subtract-hh:mm:ss-time $2 $3)
>
> Which was useful for me when I had to derush video files.
>
> HTH,