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Re: [Bug-mcron] Documentation error (every second sunday)
From: |
Mathieu Lirzin |
Subject: |
Re: [Bug-mcron] Documentation error (every second sunday) |
Date: |
Sat, 26 Jan 2019 12:48:02 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Hello Adam,
Adam Tack <address@hidden> writes:
> I think that there's an error in the Texinfo page for mcron in the
> "Every second Sunday" section:
>
> https://www.gnu.org/software/mcron/manual/mcron.html#Every-second-Sunday
>
> If the first day of the next month is a Sunday, then we should only
> *add* 7 days, so that the eighth is also a Sunday.
>
> Hence, the example should be:
>
> #+BEGIN_SRC scheme
> (job (lambda (current-time)
> (let* ((next-month (next-month-from current-time))
> (first-day (tm:wday (localtime next-month)))
> (second-sunday (if (eqv? first-day 0)
> 7
> (- 14 first-day))))
> (+ next-month (* 24 60 60 second-sunday))))
> "my-program")
> #+END_SRC
>
>
> (Arguably ~second-sunday~ as a variable name is a bit of a misnomer.)
Have you a better name in mind?
> If you wish to test this, to be sure, compare the effect of the (current)
> function when finding the second Sunday of August (with July 2, as the
> starting time), and the second Sunday of September (with August 2, as
> the starting time). (September 1 was a Sunday, while August 1 wasn't.)
Thanks for providing a test to reproduce the issue.
I was not familiar with this example in the manual, but your example
seems convincing.
I think it might be helpful to add a test case for this. Are you
interested in doing so?
> Sorry for the unsubstantial bug report, but this was driving me crazy
> while I tried to figure out what I wasn't getting (especially as it
> was "left as an exercise to the student to understand how this
> works").
Don't be sorry. I am not sure the “left as an exercise” thing is
appropriate in a software manual. :-)
Thanks
--
Mathieu Lirzin
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