From: Emanuel Berg <embe8573@student.uu.se>
To: help-gnu-emacs@gnu.org
Subject: Re: Why is booleanp defined this way?
Date: Sat, 18 Apr 2015 01:06:32 +0200 [thread overview]
Message-ID: <877ftapd6v.fsf@debian.uxu> (raw)
In-Reply-To: mailman.962.1429303822.904.help-gnu-emacs@gnu.org
jorge.alfaro-murillo@yale.edu (Jorge A.
Alfaro-Murillo) writes:
>> Of course, this "normalizes" any "truthy" value to
>> "t", but is it really needed for anything (except
>> perhaps being elegant)?
>
> Perhaps so that it returns t instead of whatever, if
> whatever is not nil.
Yes, I think this is what the OP means by
"normalizes". Normalization is a university buzzword
for example in linear algebra where two vectors are
normalized to a common coordination system so they can
be compared.
But...
(booleanp t) ; t
(booleanp nil) ; t
(booleanp 1) ; nil!
To me it looks like t and nil as arguments evaluate to
t, and everything else nil - everything else that
isn't evaluated first to either of t or nil,
of course.
The "normalization" of which you speak should rather
look something like this:
(defun normalize-boolean (obj)
(if obj t) ) ; implicit (if obj t nil)
(normalize-boolean 1) ; t
(normalize-boolean nil) ; nil
Or do you mean that `and' normalizes? It can, but that
would depend on the order:
(and 1 t) ; t
(and t 1) ; 1
So I think `booleanp' shouldn't be thought of as
a normalizer but rather as a type predicate, much like
them `stringp', `integerp', and so on.
--
underground experts united
http://user.it.uu.se/~embe8573
next prev parent reply other threads:[~2015-04-17 23:06 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 [this message]
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
[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
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=877ftapd6v.fsf@debian.uxu \
--to=embe8573@student.uu.se \
--cc=help-gnu-emacs@gnu.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.