From: Roland Winkler <winkler@gnu.org>
To: 27674@debbugs.gnu.org
Subject: bug#27674: 26.0.50; cl-progv: strange scoping due to implementation
Date: Thu, 13 Jul 2017 09:40:27 -0500 [thread overview]
Message-ID: <871spkz9gk.fsf@gnu.org> (raw)
In-Reply-To: <87lgntfhky.fsf@drachen>
On Wed, Jul 12 2017, npostavs@users.sourceforge.net wrote:
>>> > Why does the lambda still refer to the lexical binding?
>>>
>>> Maybe it would be more obvious if we wrote it like this:
>>>
>>> (let ((x 0))
>>> (cl-progv (list (intern (read-string "Enter var: "))) (list 1)
>>> (funcall (lambda () x))))
>>>
>>> Clearly the inner x must refer to the lexical let-binding, right? Even
>>> if the user happens to enter `x' at the prompt this remains true.
>>
>> Not an argument per se, because with lexical binding mode off, you can
>> surely do that.
>
> Of course, if `x' is a dynamic variable (e.g., if you use (defvar x) or
> you don't have lexical binding enabled) then the inner x refers to the
> dynamic binding (again, regardless of what the user enters at the
> prompt).
I am not sure I can follow this thread:
The docstring of cl-progv says
Bind SYMBOLS to VALUES dynamically in BODY.
But I am not sure whether this statement correctly reflects the actual
code of cl-progv: cl-progv evaluates a let form at runtime, but it is
not up to cl-progv to ensure dynamical binding. I believe it depends on
whether lexical binding is on or off whether the code currently used by
cl-progv uses dynamical binding or lexical binding.
So it is my ignorant guess that a consistent behavior of cl-progv with
lexical binding on or off requires that the bindings of SYMBOLS to
VALUES is also passed to `eval' as a second arg. From the docstring of eval:
LEXICAL can also be an actual lexical environment, in the form of an
alist mapping symbols to their value.
next prev parent reply other threads:[~2017-07-13 14:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-12 21:53 bug#27674: 26.0.50; cl-progv: strange scoping due to implementation Michael Heerdegen
2017-07-13 0:21 ` npostavs
2017-07-13 0:36 ` Michael Heerdegen
2017-07-13 0:50 ` npostavs
2017-07-13 1:11 ` Michael Heerdegen
2017-07-13 1:54 ` npostavs
2017-07-13 2:15 ` Michael Heerdegen
2017-07-13 2:41 ` npostavs
2017-07-13 14:40 ` Roland Winkler [this message]
2017-07-13 15:07 ` Noam Postavsky
2017-07-14 14:20 ` Michael Heerdegen
2017-07-15 20:46 ` Roland Winkler
2017-07-14 16:00 ` Michael Heerdegen
2017-07-19 13:55 ` Stefan Monnier
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