From: Juanma Barranquero <lekktu@gmail.com>
To: MON KEY <monkey@sandpframing.com>
Cc: 7086@debbugs.gnu.org
Subject: bug#7086: `booleanp' return value is multi-valued list
Date: Thu, 23 Sep 2010 00:35:30 +0200 [thread overview]
Message-ID: <AANLkTim5_1H+hiUHP9vi4gszpvm-vydugvjA9k7HR6fH@mail.gmail.com> (raw)
In-Reply-To: <AANLkTinm3u=qvJDd4Ncx8pyM0UZ26OzJirzyG3X2JeFn@mail.gmail.com>
On Wed, Sep 22, 2010 at 23:58, MON KEY <monkey@sandpframing.com> wrote:
> "Return non-`nil' if OBJECT is one of the two canonical boolean
> values: `t' or `nil'."
>
> It should be documented both in the manual and the docstring of `booleanp' that
> its return value is a list.
Why? It is a type predicate. If anything, it should be changed to
return t or nil, as "(elisp)2.6 Type Predicates" says:
A type predicate function takes one argument; it returns `t' if the
argument belongs to the appropriate type, and `nil' otherwise.
The fact that it returns nil or a list is an implementation detail.
> Indeed, while I can appreciate why (booleanp nil) returns a two element list
> I'm unable to reason a rationale for why (booleanp t) doesn't?
Why do you expect any kind of rationale, other than the simple fact
that it is implemented as
(memq object '(nil t)))
?
> Also, there is this goofiness:
[...]
> ; (wrong-number-of-arguments (lambda (x) (booleanp x)) 0)
What is exactly the goofiness?
> (tt--bool-nil)
> ;=> Debugger entered--Lisp error:
> ; (wrong-number-of-arguments (lambda (nil) (booleanp nil)) 0)
Again, what did you expect?
> These last two being the most maddening.
>
> Emacs lets me define the function but then accuses me of somthing I didn't even
> (appear) to do, i.e. set the constant nil.
Of course you did. Why do you expect to use `nil' as an argument and
not have trouble?
Juanma
next prev parent reply other threads:[~2010-09-22 22:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-22 21:58 bug#7086: `booleanp' return value is multi-valued list MON KEY
2010-09-22 22:35 ` Juanma Barranquero [this message]
2010-09-23 2:06 ` Kevin Rodgers
2010-09-23 10:29 ` Juanma Barranquero
2010-10-03 1:11 ` Chong Yidong
2010-09-23 4:22 ` MON KEY
2010-09-23 10:31 ` Juanma Barranquero
2010-09-23 8:12 ` Eli Zaretskii
2010-09-24 6:41 ` MON KEY
2010-09-24 8:48 ` Juanma Barranquero
2010-09-24 9:28 ` Lawrence Mitchell
2010-09-24 22:00 ` MON KEY
2010-09-25 9:18 ` Juanma Barranquero
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