From: Alex <agrambot@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 25154@debbugs.gnu.org
Subject: bug#25154: 25.1; Bindings in cl-letf are in reverse order
Date: Sat, 10 Dec 2016 13:52:34 -0600 [thread overview]
Message-ID: <87zik3wohp.fsf@gmail.com> (raw)
In-Reply-To: <838trnfxlv.fsf@gnu.org> (Eli Zaretskii's message of "Sat, 10 Dec 2016 20:27:40 +0200")
Eli Zaretskii <eliz@gnu.org> writes:
>> From: Alex <agrambot@gmail.com>
>> Cc: 25154@debbugs.gnu.org
>> Date: Sat, 10 Dec 2016 12:05:40 -0600
>>
>> > Isn't it true that the order of evaluation in a 'let' is unspecified?
>> > If you want a particular order, use 'let*'.
>>
>> I don't think so. See (info "(elisp) Local Variables"):
>>
>> All of the VALUE-FORMs in BINDINGS are evaluated in the order they
>> appear
>
> That's the evaluation order.
Yes, which is what the (nreverse binds) in my patch actually affects,
despite the name of the variable being `binds'. This is why I said that
my choice of wording for this bug report was wrong, as it focused on a
less important problem.
As said in my last email, the expression:
(cl-letf (((aref v 1) 10)
((aref w 2) 20))
(aref v 1))
expands to:
(let*
((v v)
(v w)
(old
(aref v 2))
(old
(aref v 1)))
(unwind-protect
(progn
(aset v 2 20)
(aset v 1 10)
(aref v 1))
(aset v 2 old)
(aset v 1 old)))
which does indeed evaluate the arefs and asets in reverse order. This is
the most important part of my patch.
> Your code relies on the order of
> _binding_ variables to values, which is unspecified. Contrast the
> above with the description of 'let*' below it.
Just the (nreverse simplebinds) line, which I added just to make cl-letf
a little bit saner (i.e. more like let). This part does seem to be
unspecified, but I don't see why it should unnecessarily diverge from
let.
next prev parent reply other threads:[~2016-12-10 19:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-09 23:36 bug#25154: 25.1; Bindings in cl-letf are in reverse order Alex
2016-12-10 4:29 ` Alex
2016-12-10 7:22 ` Eli Zaretskii
2016-12-10 7:43 ` Tino Calancha
2016-12-10 13:41 ` Philipp Stephani
2016-12-10 14:01 ` Tino Calancha
2016-12-10 14:09 ` Eli Zaretskii
2016-12-23 12:17 ` Philipp Stephani
2016-12-23 12:46 ` Tino Calancha
2016-12-23 13:53 ` Eli Zaretskii
2016-12-23 16:30 ` Philipp Stephani
2016-12-10 18:05 ` Alex
2016-12-10 18:14 ` npostavs
2016-12-10 19:41 ` Alex
2016-12-10 18:27 ` Eli Zaretskii
2016-12-10 19:52 ` Alex [this message]
2016-12-11 3:11 ` Tino Calancha
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