From: Noam Postavsky <npostavs@gmail.com>
To: "Clément Pit-Claudel" <clement.pitclaudel@live.com>
Cc: Michael Heerdegen <michael_heerdegen@web.de>, 31715@debbugs.gnu.org
Subject: bug#31715: cl-incf and cl-decf error out when passed a nil-valued variable as 'offset'
Date: Tue, 05 Jun 2018 19:26:51 -0400 [thread overview]
Message-ID: <87h8mg7r2c.fsf@gmail.com> (raw)
In-Reply-To: <6176bcee-a8da-8547-762b-4174652ad2a0@live.com> ("Clément Pit-Claudel"'s message of "Tue, 5 Jun 2018 19:01:56 -0400")
Clément Pit-Claudel <clement.pitclaudel@live.com> writes:
> I'm not sure what to make of the result with SBCL and CLisp, since
> (incf x nil) also fails in both of them (whereas it works for us,
> since we can't distinguish nil and unspecified).
Oh, huh, I didn't think to check that case. Maybe we should just change
cl-incf to disintguish between nil and unspecified then.
(defmacro cl-incf (place &rest args)
"Increment PLACE by X (1 by default).
PLACE may be a symbol, or any generalized variable allowed by `setf'.
The return value is the incremented value of PLACE.
\(fn PLACE &optional X)"
(declare (debug (place &optional form)))
(let* ((got-x (= (length args) 1))
(x (car args)))
(if (symbolp place)
(list 'setq place (if got-x (list '+ place x) (list '1+ place)))
(list 'cl-callf '+ place (if got-x x 1)))))
>>> In the rest of Emacs there are lots of other examples. Many of them
>>> (for example semantic-find-tags-by-name or calendar-increment-month)
>>> seem to work when passed a nil-valued variable, but many others behave
>>> like cl-incf (for example gnus-summary-article-score).
>>
>> I don't think those are great examples of macros to emulate.
>
> Agreed, I was just collecting other examples, both in support and against my point.
Yeah, I just meant we can't really use those examples either to support
or argue against your point.
next prev parent reply other threads:[~2018-06-05 23:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-04 20:06 bug#31715: cl-incf and cl-decf error out when passed a nil-valued variable as 'offset' Clément Pit-Claudel
2018-06-04 22:58 ` Noam Postavsky
2018-06-04 23:43 ` Michael Heerdegen
2018-06-05 0:12 ` Noam Postavsky
2018-06-05 0:40 ` Michael Heerdegen
2022-04-21 13:11 ` Lars Ingebrigtsen
2018-06-05 15:19 ` Clément Pit-Claudel
2018-06-05 22:53 ` Noam Postavsky
2018-06-05 23:01 ` Clément Pit-Claudel
2018-06-05 23:26 ` Noam Postavsky [this message]
2018-06-05 23:36 ` Clément Pit-Claudel
2018-06-06 0:32 ` Michael Heerdegen
2018-06-06 0:37 ` Noam Postavsky
2018-06-05 15:03 ` Clément Pit-Claudel
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