From: Eli Zaretskii <eliz@gnu.org>
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 10:12:28 +0200 [thread overview]
Message-ID: <83pqw4vpxv.fsf@gnu.org> (raw)
In-Reply-To: <AANLkTinm3u=qvJDd4Ncx8pyM0UZ26OzJirzyG3X2JeFn@mail.gmail.com>
> Date: Wed, 22 Sep 2010 17:58:12 -0400
> From: MON KEY <monkey@sandpframing.com>
> Cc:
>
> "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.
The precise form of the return value is an implementation detail.
Such details need not be documented.
Are there any _real-life_ use cases where this matter?
> Additionaly, given the nature of this function and the puposes it
> might serve, it
> should be documented _why_ the return value is a list.
Implementation details don't need to be documented, unless they really
matter to Lisp programs which use these APIs.
> Frustratingly, while the manual waxes on about the readers interpretation of
> fundamental identity equivalence w/re `nil' and `()' and their self evaluating
> specialness it has frightening little to offer w/re how one should reflect on
> these things values within lisp programs.
The manual is not a guide to reflections. Please explain what is
missing, exactly.
> 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?
Again, why is it important?
> Also, there is this goofiness:
>
> (defun tt--bool-w/opt (&optional x)
> (booleanp x))
>
> (tt--bool-w/opt nil) ;=> (nil t)
> (tt--bool-w/opt t) ;=> (t)
> (tt--bool-w/opt) ;=> (nil t)
See (info "(elisp)Argument List") for an instant enlightening: omitted
optional arguments default to nil.
> (defun tt--bool (x)
> (booleanp x))
>
> (tt--bool nil) ;=> (nil t)
> (tt--bool t) ;=> (t)
> (tt--bool 'nil) ;=> (nil t)
> (booleanp '()) ;=> (nil t)
> (booleanp ()) ;=> (nil t)
>
> (tt--bool)
> ;=> Debugger entered--Lisp error:
> ; (wrong-number-of-arguments (lambda (x) (booleanp x)) 0)
Exactly! See the above node in the manual.
But this has nothing to do with booleanp.
> 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.
Emacs gives you enough rope to hang yourself; don't do that, unless
you mean it.
next prev parent reply other threads:[~2010-09-23 8:12 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
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 [this message]
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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