From: "Óscar Fuentes" <ofv@wanadoo.es>
To: help-gnu-emacs@gnu.org
Subject: Re: (*) -> 1
Date: Wed, 18 Jan 2023 14:57:01 +0100 [thread overview]
Message-ID: <87cz7c9c9e.fsf@telefonica.net> (raw)
In-Reply-To: Y8fly8k72s+iVJYF@protected.localdomain
Jean Louis <bugs@gnu.support> writes:
> * Michael Heerdegen <michael_heerdegen@web.de> [2023-01-17 22:20]:
>> The question of use is a valid one, we missed to answer it yet. It
>> wasn't clear to me that this was part of what you are asking for.
>
> Yes, that one.
>
> Why authors decided to have (*) ➜ 1 which in case of me who could
> delete some argument like from (* tonnes quantity) I could by mistake
> delete "tonnes and quantity" and result of (*) would not be detected
> because there is no error
Throwing an error on this case is a reasonable possibility for the
language designers, but instead they decided to extend * to zero and one
arguments. Why? because it is convenient, because it makes possible to
do things like (apply '* some-list) without caring about how many
elements some-list has, which is handy when some-list comes from a place
you don't control. As far as the extension of * is reasonable, it is
nice to have, that's what the language designers thought.
So what's the reasonable extension of * (the variadic function!) to zero
arguments? Let's use some basic algebra:
(apply '* (list a b)) == (apply '* (list 1 1 a b))
which is the same as:
a * b == 1 * 1 * a * b
remove b:
a == 1 * 1 * a
remove a:
? == 1 * 1
which the same as:
(apply '* ()) == (apply '* (1 1))
or
(*) == (* 1 1)
So * applied to zero arguments shall be 1, because any other value would
break the equality.
next prev parent reply other threads:[~2023-01-18 13:57 UTC|newest]
Thread overview: 149+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-07 20:53 How to make M-x TAB not work on (interactive) declaration? Jean Louis
2023-01-07 21:11 ` Ruijie Yu via Users list for the GNU Emacs text editor
2023-01-07 23:40 ` Jean Louis
2023-01-08 6:06 ` Eli Zaretskii
2023-01-08 6:19 ` Emanuel Berg
2023-01-09 4:49 ` Jean Louis
2023-01-09 6:26 ` algorithmic Lisp language (was: Re: How to make M-x TAB not work on (interactive) declaration?) Emanuel Berg
2023-01-09 19:30 ` Jean Louis
2023-01-09 19:32 ` Jean Louis
2023-01-08 6:21 ` How to make M-x TAB not work on (interactive) declaration? Jean Louis
2023-01-08 6:32 ` Emanuel Berg
2023-01-08 10:38 ` Eli Zaretskii
2023-01-08 8:34 ` Tassilo Horn
2023-01-08 11:01 ` Eli Zaretskii
2023-01-09 13:29 ` Tassilo Horn
2023-01-08 21:35 ` Jean Louis
2023-01-08 22:35 ` [External] : " Drew Adams
2023-01-09 0:24 ` Emanuel Berg
2023-01-09 19:47 ` Jean Louis
2023-01-10 23:28 ` Emanuel Berg
2023-01-13 6:21 ` (*)->1 Jean Louis
2023-01-14 12:03 ` (*)->1 Michael Heerdegen
2023-01-14 12:33 ` (*)->1 Michael Heerdegen
2023-01-15 20:18 ` [External] : Re: How to make M-x TAB not work on (interactive) declaration? Rudolf Adamkovič
2023-01-15 20:57 ` Jean Louis
2023-01-15 22:33 ` Drew Adams
2023-01-15 23:10 ` Emanuel Berg
2023-01-16 15:28 ` Jean Louis
2023-01-16 17:07 ` Drew Adams
2023-01-16 18:25 ` Jean Louis
2023-01-17 2:20 ` Drew Adams
2023-01-17 5:28 ` tomas
2023-01-17 22:20 ` Drew Adams
2023-01-18 5:14 ` tomas
2023-01-18 5:26 ` Emanuel Berg
2023-01-19 11:38 ` tomas
2023-01-19 11:51 ` Emanuel Berg
2023-01-21 14:05 ` tomas
2023-01-23 10:14 ` Robert Pluim
2023-01-23 16:44 ` Michael Heerdegen
2023-01-23 19:28 ` tomas
2023-01-18 17:27 ` Drew Adams
2023-01-18 17:32 ` tomas
2023-01-18 14:32 ` Jean Louis
2023-01-18 20:36 ` Drew Adams
2023-01-19 9:05 ` (*) -> 1 Jean Louis
2023-01-19 9:41 ` Yuri Khan
2023-01-19 12:52 ` Anders Munch
2023-01-17 5:35 ` [External] : Re: How to make M-x TAB not work on (interactive) declaration? Jean Louis
2023-01-17 15:59 ` Yuri Khan
2023-01-17 16:42 ` Jean Louis
2023-01-17 16:05 ` Michael Heerdegen
2023-01-17 16:17 ` Yuri Khan
2023-01-17 16:25 ` tomas
2023-01-17 16:55 ` (*) -> 1 Jean Louis
2023-01-17 17:52 ` Michael Heerdegen
2023-01-17 18:11 ` Óscar Fuentes
2023-01-17 18:40 ` Jean Louis
2023-01-17 19:04 ` Óscar Fuentes
2023-01-18 13:15 ` Jean Louis
2023-01-18 14:37 ` Óscar Fuentes
2023-01-18 18:17 ` [External] : " Drew Adams
2023-01-17 19:35 ` Michael Heerdegen
2023-01-17 21:12 ` Michael Heerdegen
2023-01-17 22:01 ` Óscar Fuentes
2023-01-17 23:38 ` Michael Heerdegen
2023-01-18 7:50 ` Óscar Fuentes
2023-01-18 8:37 ` tomas
2023-01-18 12:46 ` Óscar Fuentes
2023-01-18 13:44 ` Michael Heerdegen
2023-01-18 14:07 ` Óscar Fuentes
2023-01-18 16:19 ` Andreas Eder
2023-01-18 17:14 ` Óscar Fuentes
2023-01-17 18:18 ` Jean Louis
2023-01-17 11:52 ` [External] : Re: How to make M-x TAB not work on (interactive) declaration? Michael Heerdegen
2023-01-15 21:08 ` Jean Louis
2023-01-16 5:02 ` Emanuel Berg
2023-01-16 5:38 ` tomas
2023-01-16 10:10 ` Jean Louis
2023-01-16 10:41 ` Yuri Khan
2023-01-16 15:26 ` Jean Louis
2023-01-17 4:06 ` Emanuel Berg
2023-01-17 14:00 ` tomas
2023-01-17 22:43 ` Emanuel Berg
2023-01-17 16:25 ` Nick Dokos
2023-01-17 17:19 ` Jean Louis
2023-02-11 4:38 ` Ruijie Yu via Users list for the GNU Emacs text editor
2023-02-11 10:54 ` Jean Louis
2023-01-17 17:41 ` Nick Dokos
2023-01-16 7:55 ` Yuri Khan
2023-01-16 10:16 ` Jean Louis
2023-01-16 10:37 ` Yuri Khan
2023-01-16 15:35 ` Jean Louis
2023-01-16 15:59 ` Yuri Khan
2023-01-16 16:14 ` Jean Louis
2023-01-16 16:47 ` tomas
2023-01-16 17:07 ` Drew Adams
2023-01-16 18:41 ` Jean Louis
2023-01-16 10:51 ` Anders Munch
2023-01-16 15:38 ` Jean Louis
2023-01-16 17:40 ` Andreas Eder
2023-01-16 18:17 ` tomas
2023-01-16 18:55 ` Jean Louis
2023-01-16 19:14 ` tomas
2023-01-16 18:46 ` Jean Louis
2023-01-17 2:37 ` Eduardo Ochs
2023-01-17 5:46 ` (*) -> 1 Jean Louis
2023-01-17 15:56 ` Michael Heerdegen
2023-01-17 16:29 ` Jean Louis
2023-01-17 16:43 ` tomas
2023-01-17 17:25 ` Jean Louis
2023-01-17 19:11 ` Nick Dokos
2023-01-17 17:17 ` Michael Heerdegen
2023-01-17 17:26 ` Jean Louis
2023-01-17 18:46 ` Michael Heerdegen
2023-01-17 18:51 ` Jean Louis
2023-01-17 18:04 ` Jean Louis
2023-01-17 18:28 ` Eduardo Ochs
2023-01-17 19:18 ` Michael Heerdegen
2023-01-18 12:27 ` Jean Louis
2023-01-18 13:37 ` Michael Heerdegen
2023-01-19 8:20 ` Jean Louis
2023-01-19 10:06 ` Tassilo Horn
2023-01-19 13:43 ` Michael Heerdegen
2023-01-19 14:42 ` Jean Louis
2023-01-19 15:27 ` tomas
2023-01-18 13:57 ` Óscar Fuentes [this message]
2023-01-19 8:32 ` Jean Louis
2023-01-19 16:51 ` Óscar Fuentes
2023-01-20 8:01 ` Jean Louis
2023-01-18 14:25 ` Michael Heerdegen
2023-01-19 8:34 ` Jean Louis
2023-01-19 13:54 ` Michael Heerdegen
2023-01-19 14:54 ` Jean Louis
2023-01-19 15:19 ` Tassilo Horn
2023-01-19 15:46 ` Michael Heerdegen
2023-01-19 17:38 ` Dr Rainer Woitok
2023-01-20 7:31 ` Jean Louis
2023-01-20 11:49 ` Dr Rainer Woitok
2023-01-19 17:44 ` [External] : " Drew Adams
2023-01-19 21:29 ` Michael Heerdegen
2023-01-20 7:40 ` Jean Louis
2023-01-20 8:47 ` Emanuel Berg
2023-01-18 9:02 ` Anders Munch
2023-01-18 10:49 ` Michael Heerdegen
2023-01-18 11:10 ` Emanuel Berg
2023-01-18 12:48 ` Eli Zaretskii
2023-01-18 14:29 ` Michael Heerdegen
[not found] ` <87k01lica7.fsf@eder.anydns.info>
2023-01-17 16:04 ` Jean Louis
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