From: Rusi <rustompmody@gmail.com>
To: help-gnu-emacs@gnu.org
Subject: Re: Why is booleanp defined this way?
Date: Fri, 17 Apr 2015 19:01:11 -0700 (PDT) [thread overview]
Message-ID: <ac0769a5-9262-4bb7-a305-5c2f0c9b0b88@googlegroups.com> (raw)
In-Reply-To: <mailman.946.1429302909.904.help-gnu-emacs@gnu.org>
On Saturday, April 18, 2015 at 2:05:11 AM UTC+5:30, Marcin Borkowski wrote:
> Hi all,
>
> this is what I found in subr.el:
>
> ,----
> | (defun booleanp (object)
> | "Return t if OBJECT is one of the two canonical boolean values: t or nil.
> | Otherwise, return nil."
> | (and (memq object '(nil t)) t))
> `----
>
> Seemingly, it doesn't make much sense: what is the purpose of saying
>
> (and (whatever) t)
>
> instead of just
>
> (whatever)
>
> for a predicate? Of course, this "normalizes" any "truthy" value to
> "t", but is it really needed for anything (except perhaps being
> elegant)?
>
> Best,
Elisp does not have a proper boolean type; unlike say symbols with
symbolp, strings with stringp, numberp -- some union of numeric types etc.
However programmers need boolean in their ontology even if (and even more if)
the language does not support it.
I'd say booleanp is a hesitant step towards supporting boolean in the ontology
without supporting it in the language.
next prev parent reply other threads:[~2015-04-18 2:01 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.946.1429302909.904.help-gnu-emacs@gnu.org>
2015-04-17 20:55 ` Why is booleanp defined this way? 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 [this message]
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
2015-04-17 20:34 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
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