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From: Jean Louis <bugs@gnu.support>
To: Andreas Eder <a_eder_muc@web.de>
Cc: help-gnu-emacs@gnu.org
Subject: (*) -> 1
Date: Tue, 17 Jan 2023 19:04:02 +0300	[thread overview]
Message-ID: <Y8bG8rmvEXY0jSfm@protected.localdomain> (raw)
In-Reply-To: <87k01lica7.fsf@eder.anydns.info>

* Andreas Eder <a_eder_muc@web.de> [2023-01-17 15:20]:
> > For now vague purpose is only to satisfy some other functions which
> > process lists, like `reduce' or `apply', I am searching for
> > confirmation if that was the sole purpose.
> 
> The purpose is to be consistent in a mathematical sense.
> There empty products are 1 and empty sums are 0. That is the only to
> sensibly define it and to  fulfill the associative property of the
> operations.

There are different contexts:

- mathematical sense whereby "+" always require addends, without it,
  there is nothing to add. A number like zero is alright, but it must
  be there.

- in lisp no addend is needed to yield (+) ➜ 0

- there is convention of identity elements, fine, but I do not see
  relation to above, neither why is one convention nullified in favor
  of the other convention

Then we have:

- mathematical sense whereby "*" always require 2 factos, without it,
  there is nothing to multiply. That is also convention. 

- in lisp no factor is needed to yield (*) ➜ 1

- because some other convention is followed nullyfing the previously
  explained one.

Still I have not find clear relation why is it so.

It is definitely not in every Lisp that way.

PicoLisp does not think so:

$ pil
: (+)
-> NIL
: (*)
-> NIL

and it handles properly function `apply' without having (+) ➜ 0:
----------------------------------------------------------------

: (apply '+ '(1 2 3 4))
-> 10

(apply '* '(1 2 3 4))
-> 24

Emacs Lisp:

(-) ➜ 0

but Guile:

-)
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Wrong number of arguments to -

So there are differences and the question is still open why is Lisp
using those identity elements.

-- 
Jean

Take action in Free Software Foundation campaigns:
https://www.fsf.org/campaigns

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https://stallmansupport.org/



      parent reply	other threads:[~2023-01-17 16:04 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
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 [this message]

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