From: Tassilo Horn <tsdh@gnu.org>
To: Marcin Borkowski <mbork@mbork.pl>
Cc: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
Subject: Re: Why is booleanp defined this way?
Date: Sat, 18 Apr 2015 08:13:26 +0200 [thread overview]
Message-ID: <87d2323qwp.fsf@gnu.org> (raw)
In-Reply-To: <87siby7au6.fsf@mbork.pl> (Marcin Borkowski's message of "Fri, 17 Apr 2015 22:34:45 +0200")
Marcin Borkowski <mbork@mbork.pl> writes:
Hi Marcin,
> Of course, this "normalizes" any "truthy" value to "t", but is it
> really needed for anything (except perhaps being elegant)?
It's just as you say and the others already explained. And then have a
look where and `booleanp` is actually used. Basically all usages in
emacs itself are
(put 'some-variable 'safe-local-variable 'booleanp)
So some-variable is safe as a file-local variable only if it is either
nil or t but it is not safe when its value is (eval (shell-command "rm
-rf ~/")).
Another use-case is when you are talking to some external service that
wan't "real" (aka, non-generalized booleans) and use some marshalling
code which automatically converts nil to false and t to true.
Bye,
Tassilo
next prev parent reply other threads:[~2015-04-18 6:13 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-17 20:34 Why is booleanp defined this way? Marcin Borkowski
2015-04-17 20:49 ` Jorge A. Alfaro-Murillo
[not found] ` <mailman.962.1429303822.904.help-gnu-emacs@gnu.org>
2015-04-17 23:06 ` Emanuel Berg
2015-04-18 0:41 ` Pascal J. Bourguignon
2015-04-18 1:06 ` Emanuel Berg
2015-04-18 1:23 ` Pascal J. Bourguignon
2015-04-18 7:44 ` Marcin Borkowski
2015-04-18 8:37 ` Stefan Nobis
2015-04-19 23:15 ` Emanuel Berg
2015-04-18 2:37 ` Drew Adams
2015-04-18 6:13 ` Tassilo Horn [this message]
[not found] <mailman.946.1429302909.904.help-gnu-emacs@gnu.org>
2015-04-17 20:55 ` Pascal J. Bourguignon
2015-04-17 23:20 ` Barry Margolin
2015-04-17 23:30 ` Emanuel Berg
2015-04-18 0:43 ` Pascal J. Bourguignon
2015-04-18 3:13 ` Barry Margolin
2015-04-18 3:12 ` Barry Margolin
2015-04-18 2:01 ` Rusi
2015-04-18 2:23 ` Emanuel Berg
2015-04-18 2:33 ` Rusi
2015-04-18 2:55 ` Emanuel Berg
2015-04-18 3:11 ` Barry Margolin
2015-04-18 3:35 ` Rusi
2015-04-18 4:56 ` Barry Margolin
2015-04-19 23:08 ` Emanuel Berg
2015-04-19 23:00 ` Emanuel Berg
2015-04-18 21:24 ` Emanuel Berg
2015-04-18 7:52 ` Marcin Borkowski
[not found] ` <mailman.997.1429343558.904.help-gnu-emacs@gnu.org>
2015-04-18 12:43 ` Rusi
2015-04-18 4:09 ` Pascal J. Bourguignon
2015-04-18 5:00 ` Rusi
2015-04-18 3:50 ` Pascal J. Bourguignon
2015-04-18 5:03 ` Stefan Monnier
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