all messages for Emacs-related lists mirrored at yhetil.org
 help / color / mirror / code / Atom feed
From: Drew Adams <drew.adams@oracle.com>
To: Heime <heimeborgia@protonmail.com>
Cc: Emanuel Berg <incal@dataswamp.org>,
	"help-gnu-emacs@gnu.org" <help-gnu-emacs@gnu.org>
Subject: RE: [External] : Re: cond construct for situation when a variable is t
Date: Tue, 22 Aug 2023 21:07:24 +0000	[thread overview]
Message-ID: <SJ0PR10MB5488723FCAAC375BFE38821DF31FA@SJ0PR10MB5488.namprd10.prod.outlook.com> (raw)
In-Reply-To: <oQH90tKTwMXzdSFS0rnnqTCD-3tIDz4nAZaafUvVncXwQqdqqNoDtYEahx2c8bSeVihDQ2vZEP5_kN9wi8ycS7npRgUOW0iBdgxuwWd4VxI=@protonmail.com>

> > > There is no 'boolean datatype' in elisp.
> > > With nil and empty list () being false,
> > > anything else is true.
> >
> >
> > There's no real true or false in Lisp. But yes,
> > that's the convention, and that convention is
> > baked into primitive conditionals, such as `if' and` cond'. So sure, you
> can think of it as
> > being more than a convention.
> >
> > > That t is used for true, is that by convention ?
> > > Should t be used, or is it unreliable ?
> >
> >
> > Just like the "convention" described above, it's
> > a convention. But also just like it, it's baked
> > into primitives. So yes, the constant `t' is a
> > typical non-nil value used by conditionals to
> > represent "true". And it's the canonical way to
> > represent "true", meaning that it's the clearest
> > way to tell human readers of code that "true" is
> > meant.
> 
> The canonical convention also stipulates that the symbol
> t is not to be modified to something else though, am I right ?

Dunno why it would stipulate that, as trying to
change its value raises an error, as I showed.

You can do practically anything in Lisp, so maybe
there's a way to change its value (you can certainly
change the value of a symbol `t' in a different
obarray, but that's not what we're talking about).

  reply	other threads:[~2023-08-22 21:07 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-18 14:00 cond construct for situation when a variable is t Heime
2023-08-19 22:04 ` Emanuel Berg
2023-08-22 12:18   ` Heime
2023-08-22 16:10     ` [External] : " Drew Adams
2023-08-22 19:31       ` Emanuel Berg
2023-08-23 19:49         ` Drew Adams
2023-08-22 19:29     ` Emanuel Berg
2023-08-22 12:32   ` Heime
2023-08-22 16:17     ` [External] : " Drew Adams
2023-08-22 20:21       ` Heime
2023-08-22 21:07         ` Drew Adams [this message]
2023-08-19 22:43 ` Rudolf Adamkovič

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=SJ0PR10MB5488723FCAAC375BFE38821DF31FA@SJ0PR10MB5488.namprd10.prod.outlook.com \
    --to=drew.adams@oracle.com \
    --cc=heimeborgia@protonmail.com \
    --cc=help-gnu-emacs@gnu.org \
    --cc=incal@dataswamp.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this external index

	https://git.savannah.gnu.org/cgit/emacs.git
	https://git.savannah.gnu.org/cgit/emacs/org-mode.git

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.