GNU bug report logs - #25540
notice issue in expand -- doesn't allow for expressing tabsize value in tabstop(s)

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Message #23 received at 25540 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Reuti <reuti <at> staff.uni-marburg.de>
Cc: L A Walsh <coreutils <at> tlinx.org>, 25540 <at> debbugs.gnu.org
Subject: Re: bug#25540: notice issue in expand -- doesn't allow for expressing
 tabsize value in tabstop(s)
Date: Sun, 26 Feb 2017 15:44:18 -0800

[Message part 1 (text/plain, inline)]

On 26/01/17 03:27, Reuti wrote:
> 
>> Am 26.01.2017 um 12:04 schrieb Pádraig Brady <P <at> draigBrady.com>:
>>
>> On 26/01/17 10:26, Reuti wrote:
>>>
>>>> Am 26.01.2017 um 05:29 schrieb L A Walsh <coreutils <at> tlinx.org>:
>>>>
>>>>
>>>> In programs that take tabstops, as an alternative to a tabsize, I've always
>>>> seen tabs beyond the end of the list taken as equal to the highest tab-stop
>>>> difference.  So for a tabsize=8, a tabset of 1,9 would be equivalent -- with
>>>> tabs above "9" being "9-1" or every 8th column above 9.
>>>>
>>>> Otherwise you have no way of expression all tabs on a line that stretches out to
>>>> "???" 160? 240? what? other than to enumerate tabstops to infinity.
>>>>
>>>> If they want to limit tabstops above the last to size "1", they can use something like 1,9,10.  How else can one specify tabs beyond the last
>>>> for a size other than "1"?
>>>>
>>>> Could this be changed/fixed?
>>>
>>> For now the behavior is like specified on the info page: "[…] and replace any tabs beyond the last tab stop given with single spaces." To avoid that this gets broken, I would suggest to use a modified syntax like 1,9,30,34,/4 for using a width of 4 beyond 34.
>>>
>>
>> I like that. Explicit and extensible.
>> An alternative could be: --tabs=1,9,30,34,+4 ?
> 
> Sure, this works too. In fact: I had this also in mind first, but with the extension to specify a multiplicator for the width I found "2+4" misleading and a slash more appropriate.
> 

Even without the multiplier a '+' would be misleading
since we wouldn't be necessarily adding that to the last value.

The attached uses your suggestion of '/' but only allowed in the last position.

thanks,
Pádraig.

[expand-trailing-tabsize.patch (text/x-patch, attachment)]

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