From: MON KEY <monkey@sandpframing.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: lekktu@gmail.com, cyd@stupidchicken.com, schwab@linux-m68k.org,
6878@debbugs.gnu.org
Subject: bug#6878: bool-vectors of length 0 signal error when aref/aset the 0th element
Date: Fri, 20 Aug 2010 14:44:12 -0400 [thread overview]
Message-ID: <AANLkTimOco308axeejAm_Q5yaXZ_RLmi9EBj4y8vNnzY@mail.gmail.com> (raw)
In-Reply-To: <jwvtympv3p0.fsf-monnier+emacs@gnu.org>
On Fri, Aug 20, 2010 at 9:02 AM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> As you wish. Though, I don't think changing the wording solves the
>> real problem If there are no good reasons to create a boole-vectro of
>> length 0 why allow it?
>
> That's the wrong question. The question is: why not allow them?
How about Juanma's example earlier wich is a mis-application of substring on
vectors satisfying the predicate `bool-vector-p' e.g. his:
> (defun split-vec (v p)
> (list (substring v 0 p)
> (substring v p (length v))))
>
>> Emacs lisp doesn't and I can think of no good reasons to create 0
>> length bool-vectors.
>> Can any one else?
>
> The same reasons to create zero-length strings.
>
I'm not convinced.
Anyhow, my query included the caveat "good reasons" :)
(substring (make-bool-vector 0 t) 0)
;=> Debugger entered--Lisp error: (wrong-type-argument arrayp #&0"")
And, it doesn't really work for vectors either:
(substring (make-vector 0 1) 0)
;=> []
Likewise, where is the sense in these:
(apply 'string (append (make-bool-vector 0 t) nil))
;=> ""
(concat (make-bool-vector 0 t))
;=> ""
When this:
(concat)
;=> ""
and this:
(apply 'string nil)
;=> ""
would suffice.
Note, I _do_ recognize that there is some utility for things like this w/
_vanilla_ vectors:
(defmacro v->empty (&optional char-val-maybe)
(let ((vvoid (make-symbol "vvoid")))
`(let ((,vvoid (if (characterp ,char-val-maybe)
1 0)))
(make-vector ,vvoid ,char-val-maybe))))
(v->empty 'not-a-char)
;=> []
(v->empty 32)
;=> [32]
(v->empty)
;=> []
(mapconcat #'identity
(mapcar #'(lambda (ve) (concat (v->empty ve)))
'(119 'not-a-char 32 nil 111 'nor-inil
32 "nope" 119 'nada 33)) "")
But I can't see how the `make-vector' idiom would translate for
`make-bool-vector'.
> Stefan
>
--
/s_P\
next prev parent reply other threads:[~2010-08-20 18:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-18 4:19 bug#6878: bool-vectors of length 0 signal error when aref/aset the 0th element MON KEY
2010-08-18 7:36 ` Stefan Monnier
2010-08-19 1:51 ` MON KEY
2010-08-19 8:42 ` Andreas Schwab
2010-08-19 14:13 ` MON KEY
2010-08-19 15:51 ` Stefan Monnier
2010-08-19 17:06 ` MON KEY
2010-08-19 14:47 ` Stefan Monnier
2010-08-19 15:04 ` Andreas Schwab
2010-08-19 16:18 ` Chong Yidong
2010-08-19 17:09 ` MON KEY
2010-08-19 18:40 ` Juanma Barranquero
2010-08-19 23:24 ` Chong Yidong
2010-08-20 2:01 ` MON KEY
2010-08-20 2:23 ` Juanma Barranquero
2010-08-20 18:01 ` MON KEY
2010-08-20 19:49 ` Juanma Barranquero
2010-08-20 23:06 ` MON KEY
2010-08-20 13:02 ` Stefan Monnier
2010-08-20 18:44 ` MON KEY [this message]
2010-08-21 12:40 ` Kevin Rodgers
2010-08-21 15:53 ` Andreas Schwab
2010-08-21 17:02 ` MON KEY
2010-08-18 8:36 ` Andreas Schwab
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