From: Bozhidar Batsov <bozhidar@batsov.com>
To: Eli Zaretskii <eliz@gnu.org>,
Stefan Monnier <monnier@iro.umontreal.ca>,
nandryshak@gmail.com, Nicolas Petton <nicolas@petton.fr>,
emacs-devel <emacs-devel@gnu.org>
Subject: Re: string> missing?
Date: Thu, 4 Jun 2015 09:02:05 +0200 [thread overview]
Message-ID: <CAM9Zgm2429mCXiJtzg=kD3rOjvLtgKgLNcz2icT9zLVcwH9RTA@mail.gmail.com> (raw)
In-Reply-To: <87vbf4dldj.fsf@gnu.org>
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Way too much bikeshedding for something super trivial. Let's add the
function(s) and be done with it.
On 4 June 2015 at 08:43, Tassilo Horn <tsdh@gnu.org> wrote:
> Eli Zaretskii <eliz@gnu.org> writes:
>
> >> Emacs is inconsistent. That's part of its inheritance.
> >> If someone wants to add string>, I'm perfectly OK with it.
> >
> > Why not _remove_ string< and use compare-strings for both jobs?
>
> Oh yes, please. Everybody wants to use a function of 6-7 arguments! ;-)
>
> Fun aside: aside from the reason of symmertry/consistency, I can see at
> least two practical advantages of having `string>'. Whenever it should
> be used as predicate of a higher-order function,
>
> (sort coll #'string>)
>
> is more concise than
>
> (sort coll (lambda (a b) (string< b a)))
>
> and it is also better to edebug because you are usually not
> interested in edebugging the lambda. (What can possibly go wrong
> there?!?)
>
> However, this is true for any other simple predicate aside from number
> or string comparison. So I'd suggest to have a `complement' function
> which simply returns a function negating the value of some predicate,
> e.g.,
>
> (defun complement (fn)
> "Returns a function calling FN and returning FN's negated value."
> (lambda (&rest args)
> (not (apply fn args))))
>
> Then you can do
>
> (sort coll (complement #'string<))
>
> which looks like a good compromise wrt conciseness and edebuggability.
> Of course, (complement #'string<) is string>= which will work fine for
> `sort' but probably not for other higer-order functions.
>
> Grepping the emacs source code, there are indeed at least three
> occurrences of (nreverse (sort coll predicate)) which could make use of
> that. And I can also find occurrences of (lambda (a b) (string< b a)).
> However, when the number of definitions is what makes a function which
> is currently not provided by Elisp important, than it looks to me that
> there should be a function for
>
> (lambda (a b) (string< (car a) (car b)))
>
> For that, `rgrep' delivers 40 matches in the elisp repositories I have
> on my disk, and I only searched for
>
> "(lambda (. .) (string< (car .) (car .)))"
>
> so it has to occur on one line with the exact spacing and 1-char wide
> arguments. So that suggests we want to have a
> `car-string-less-than-car' (or indeed want to have the numerical
> comparison functions work for strings, too, as Stefan suggested because
> there's already `car-less-than-car').
>
> Bye,
> Tassilo
>
>
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next prev parent reply other threads:[~2015-06-04 7:02 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-03 9:05 string> missing? Nicolas Petton
2015-06-03 14:51 ` Eli Zaretskii
2015-06-03 15:03 ` Nicolas Petton
2015-06-03 15:26 ` Tassilo Horn
2015-06-03 15:46 ` Nick Andryshak
2015-06-03 15:55 ` Eli Zaretskii
2015-06-03 16:10 ` Nick Andryshak
2015-06-03 16:42 ` Eli Zaretskii
2015-06-03 16:50 ` Nick Andryshak
2015-06-03 18:10 ` Andreas Schwab
2015-06-03 19:13 ` Alan Mackenzie
2015-06-03 19:13 ` Eli Zaretskii
2015-06-03 19:34 ` Nick Andryshak
2015-06-03 19:53 ` Eli Zaretskii
2015-06-03 20:11 ` Nick Andryshak
2015-06-03 20:37 ` Jay Belanger
2015-06-03 20:53 ` Nick Andryshak
2015-06-03 21:35 ` Jay Belanger
2015-06-03 21:36 ` Thibaut Verron
2015-06-03 22:25 ` Stefan Monnier
2015-06-04 5:30 ` Thibaut Verron
2015-06-04 7:44 ` Nicolas Richard
2015-06-04 8:08 ` Thibaut Verron
2015-06-04 15:33 ` Stefan Monnier
2015-06-03 22:28 ` Stefan Monnier
2015-06-04 2:50 ` Eli Zaretskii
2015-06-04 6:43 ` Tassilo Horn
2015-06-04 7:02 ` Bozhidar Batsov [this message]
2015-06-04 7:53 ` Gnus & Mail-Followup-To (was: string> missing?) Nicolas Richard
2015-06-04 9:04 ` Gnus & Mail-Followup-To Tassilo Horn
2015-06-04 12:50 ` Nicolas Richard
2015-06-05 17:07 ` Tassilo Horn
2015-06-06 8:48 ` Nicolas Richard
2015-06-04 4:20 ` string> missing? Thierry Volpiatto
2015-06-04 15:52 ` Nicolas Petton
2015-06-03 21:24 ` Richard Stallman
2015-06-04 15:07 ` Eli Zaretskii
2015-06-05 17:56 ` Richard Stallman
2015-06-05 19:04 ` Eli Zaretskii
2015-06-05 20:40 ` Tassilo Horn
2015-06-05 21:35 ` Ivan Shmakov
2015-06-05 21:53 ` Tassilo Horn
2015-06-05 22:04 ` Tassilo Horn
2015-06-06 6:40 ` Eli Zaretskii
2015-06-06 8:53 ` Tassilo Horn
2015-06-07 0:28 ` Richard Stallman
2015-06-06 1:52 ` Richard Stallman
2015-06-06 7:57 ` Eli Zaretskii
2015-06-07 0:28 ` Richard Stallman
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