From: Nicolas Petton <nicolas@petton.fr>
To: tzz@lifelogs.com
Cc: help-gnu-emacs@gnu.org
Subject: Re: plists, alists, and hashtables (was: How to iterate over properties in a plist?)
Date: Tue, 4 Aug 2015 10:29:04 +0000 [thread overview]
Message-ID: <p8wlne.nsjzsj.1hge0xg-qmf@mail.messagingengine.com> (raw)
In-Reply-To: <87a8u7we9s.fsf_-_@lifelogs.com>
On Tue Aug 4 11:15:27 2015 GMT+0100, Ted Zlatanov wrote:
> On Sat, 01 Aug 2015 18:49:38 -0400 Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> SM> - plists need to be "parsed" in order to figure out if an element is a key
> SM> or a value.
>
> That's true, but there's some idea that a plist is "correct" if it can
> be parsed. It's also visually easier to parse, I think, especially for
> beginners. Also, symbol plists are pretty well ensconced at the C level.
>
> By contrast, alists don't have a strong structure and parsing them is
> not simple for beginners. For instance:
>
> (alist-get 'a '((a) (b 1) (c . 2) d)) -> nil
> (alist-get 'b '((a) (b 1) (c . 2) d)) -> (1)
> (alist-get 'c '((a) (b 1) (c . 2) d)) -> 2
> (alist-get 'd '((a) (b 1) (c . 2) d)) -> nil ; no error
>
> The real map type in Emacs Lisp is the hashtable, I think. But because
> of historical baggage, we end up discussing the benefits of two list
> formats when used as maps. Which feels like discussing which of two
> different bicycles is better for carrying 5 people.
>
> For instance, the hashtable keys are unambiguously
> (hash-table-keys my-hashtable) and there's no looping or parsing.
>
> I wonder, if hashtables had a better reader syntax (like plists or
> alists) and better Customize support, would they see wider use?
The new map.el library provides a common interface for both hashtables and alists (as well as other key/value data structures). Maybe that will make it easier for people to use hashtables?
Cheers,
Nico
next prev parent reply other threads:[~2015-08-04 10:29 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-31 21:42 How to iterate over properties in a plist? Marcin Borkowski
2015-07-31 22:18 ` Stefan Monnier
2015-07-31 22:29 ` Marcin Borkowski
2015-07-31 22:42 ` Dmitry Gutov
2015-08-01 13:34 ` Michael Heerdegen
[not found] ` <mailman.7705.1438381807.904.help-gnu-emacs@gnu.org>
2015-07-31 23:33 ` Pascal J. Bourguignon
2015-08-01 22:49 ` Stefan Monnier
[not found] ` <mailman.7750.1438469396.904.help-gnu-emacs@gnu.org>
2015-08-04 10:15 ` plists, alists, and hashtables (was: How to iterate over properties in a plist?) Ted Zlatanov
2015-08-04 10:29 ` Nicolas Petton [this message]
[not found] ` <mailman.7809.1438684158.904.help-gnu-emacs@gnu.org>
2015-08-04 11:23 ` plists, alists, and hashtables Ted Zlatanov
2015-08-05 4:36 ` plists, alists, and hashtables (was: How to iterate over properties in a plist?) Rusi
2015-08-05 6:12 ` plists, alists, and hashtables Pascal J. Bourguignon
2015-08-05 9:47 ` Ted Zlatanov
2015-08-05 12:20 ` Rusi
2015-08-06 19:16 ` Stefan Monnier
[not found] ` <mailman.7892.1438888819.904.help-gnu-emacs@gnu.org>
2015-08-07 16:33 ` Rusi
2015-08-05 17:24 ` Pascal J. Bourguignon
2015-08-05 18:31 ` Ted Zlatanov
2015-08-05 19:30 ` Barry Margolin
2015-08-05 19:40 ` Robert Thorpe
2015-08-05 21:11 ` Pascal J. Bourguignon
2015-08-06 15:17 ` Ted Zlatanov
2015-08-06 18:46 ` Pascal J. Bourguignon
2015-08-06 20:19 ` Drew Adams
2015-08-06 21:08 ` Ted Zlatanov
2015-08-07 0:23 ` Pascal J. Bourguignon
2015-08-06 19:35 ` Stefan Monnier
2015-08-05 13:48 ` Drew Adams
2015-08-06 19:12 ` Stefan Monnier
[not found] ` <mailman.7890.1438888393.904.help-gnu-emacs@gnu.org>
2015-08-06 20:00 ` Pascal J. Bourguignon
2015-08-06 20:57 ` Ted Zlatanov
2015-08-06 21:10 ` Drew Adams
[not found] ` <mailman.7902.1438895429.904.help-gnu-emacs@gnu.org>
2015-08-06 21:15 ` Ted Zlatanov
2015-08-06 21:31 ` Stefan Monnier
2015-08-07 1:53 ` Ted Zlatanov
2015-08-07 7:34 ` Pascal J. Bourguignon
2015-08-07 16:32 ` Stefan Monnier
[not found] ` <mailman.7941.1438965165.904.help-gnu-emacs@gnu.org>
2015-08-08 3:48 ` Pascal J. Bourguignon
2015-08-08 13:42 ` Stefan Monnier
2015-08-08 14:51 ` Rusi
2015-08-07 0:08 ` Pascal J. Bourguignon
2015-08-07 2:14 ` Ted Zlatanov
2015-08-07 7:53 ` Pascal J. Bourguignon
2015-08-07 11:21 ` Ted Zlatanov
2015-08-07 11:47 ` Pascal J. Bourguignon
2015-08-07 17:21 ` Ted Zlatanov
2015-08-07 19:21 ` Stefan Monnier
[not found] ` <mailman.7952.1438975314.904.help-gnu-emacs@gnu.org>
2015-08-08 3:52 ` Pascal J. Bourguignon
2015-08-07 16:35 ` Stefan Monnier
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