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).
next prev parent 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
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