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From: Nick Dokos <ndokos@gmail.com>
To: emacs-orgmode@gnu.org
Subject: Re: Incorrect sum of times in table
Date: Mon, 01 Jul 2013 16:49:08 -0400	[thread overview]
Message-ID: <87ppv2atvf.fsf@gmail.com> (raw)
In-Reply-To: CAMJKaZym2M9n5vpudT_3NLpxcQvoiHYwj0uG8bVypHhtZOcu0Q@mail.gmail.com

Paul Stansell <paulstansell@gmail.com> writes:

> Hello,
>
> I noticed a case where the sum of two times in a table does not give
> the correct answer.
>
> To see this, create an org file with the following lines:
>
> | 0:00:31 |
> | 0:00:30 |
> |---------|
> |         |
>
> Open it and type C-+ C-y in the empty cell of the table.  The answer
> inserted is 0:01:00 instead of 0:01:01.
>

I think you mean C-c +.

The problem is that these things are calculated as decimal hours, using
floating point arithmetic and you get truncation towards 0 when the
value is printed out as an integer. The format in org-table-sum is

    (format "%d:%02d:%02d" h m s)

but s is 0.9999...  and it gets formatted as 0.

It might be better to use

    (format "%.0f:%02.0f:%02.0f" h m s)

i.e. as floating point with no places after the decimal point
(in which case the decimal point does not seem to be output).
But there may be other problems that I have not thought of.
It might be even better to round the floating point number to
the nearest integer and use %d formats instead:

    (format "%d:%02d:%02d" (round h) (round m) (round s))

-- 
Nick

next prev parent reply	other threads:[~2013-07-01 20:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-01 17:38 Incorrect sum of times in table Paul Stansell
2013-07-01 20:49 ` Nick Dokos [this message]
2013-07-01 21:22   ` Bastien
2013-07-03  8:18     ` Bastien

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