From: Paul Eggert <eggert@cs.ucla.edu>
To: Lars Ingebrigtsen <larsi@gnus.org>
Cc: emacs-devel@gnu.org
Subject: Re: master 71783e9: Add the string-numeric-lessp function
Date: Sun, 21 Feb 2016 20:16:56 -0800 [thread overview]
Message-ID: <56CA8BB8.6040908@cs.ucla.edu> (raw)
In-Reply-To: <87twl1xul1.fsf@gnus.org>
Lars Ingebrigtsen wrote:
> I don't think that's something our numerical string comparison function
> should be doing.
Again, I'm not sure I'm following. The two strings "2.21-0ubuntu4" and
"2.21-0ubuntu4.1" are identical except the latter has ".1" appended. Shouldn't
almost any sane kind of string comparison consider the shorter to be less than
the longer?
If only some strings are valid for comparison, I suppose the comparison function
could be a partial function, e.g., it could signal an error when given a string
that it doesn't think has a valid format. This of course could be done, but it
makes usage more complicated. For sorting, having comparison functions be total
functions is much simpler to explain.
At least, that's been the tradition in other GNU tools. GNU ls -v applies the
string-version-lessp algorithm to every pair of file names that it considers,
and it works on arbitrary file names. It sounds like you may be thinking of some
other tradition, although I'm not sure what that tradition would be.
The GNU ls -v approach works well in practice, because people who care about
version numbers tend to name their files consistently. E.g., they do not put
files "foo001.png" "foo1.png" in the same directory, because that kind of usage
would confuse humans no matter what 'ls -v' does.
next prev parent reply other threads:[~2016-02-22 4:16 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20160221043348.25201.81719@vcs.savannah.gnu.org>
[not found] ` <E1aXLiO-0006ZB-4R@vcs.savannah.gnu.org>
2016-02-21 4:43 ` master 71783e9: Add the string-numeric-lessp function Lars Ingebrigtsen
2016-02-21 5:36 ` Lars Ingebrigtsen
2016-02-21 6:15 ` Stephan Mueller
2016-02-21 10:02 ` Lars Ingebrigtsen
2016-02-21 19:35 ` Yuri Khan
2016-02-22 2:51 ` Lars Ingebrigtsen
2016-02-22 17:59 ` Richard Stallman
2016-02-21 21:30 ` Paul Eggert
2016-02-22 1:32 ` Andy Moreton
2016-02-22 4:01 ` Paul Eggert
2016-02-22 16:11 ` Eli Zaretskii
2016-02-22 2:53 ` Lars Ingebrigtsen
2016-02-22 3:50 ` Paul Eggert
2016-02-22 4:00 ` Lars Ingebrigtsen
2016-02-22 4:16 ` Paul Eggert [this message]
2016-02-22 4:22 ` Lars Ingebrigtsen
2016-02-22 5:56 ` Paul Eggert
2016-03-07 0:16 ` Juri Linkov
2016-03-07 0:53 ` Paul Eggert
2016-03-07 17:45 ` Richard Stallman
2016-03-07 17:49 ` Lars Magne Ingebrigtsen
2016-03-07 23:55 ` Juri Linkov
2016-03-07 23:52 ` Juri Linkov
2016-03-08 2:06 ` Paul Eggert
2016-03-08 9:26 ` Andreas Schwab
2016-03-09 9:26 ` Paul Eggert
2016-03-07 2:27 ` Drew Adams
2016-03-07 21:14 ` Johan Bockgård
2016-03-07 22:03 ` Drew Adams
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