From: David Kastrup <dak@gnu.org>
To: Kelly Dean <kelly@prtime.org>
Cc: "Stephen J. Turnbull" <stephen@xemacs.org>, emacs-devel@gnu.org
Subject: Re: Rant - Elisp terminology is deceptive
Date: Sat, 24 Jan 2015 12:03:08 +0100 [thread overview]
Message-ID: <87vbjw4f0z.fsf@fencepost.gnu.org> (raw)
In-Reply-To: <vSBKENd7ygMsRVo8YjOrZAZSstXQJbLtz3H5b5z1Zsv@local> (Kelly Dean's message of "Sat, 24 Jan 2015 10:30:59 +0000")
Kelly Dean <kelly@prtime.org> writes:
> Stephen J. Turnbull wrote:
>> Buffer-local values are global values in the usual
>> sense that they are instance-wide and can be accessed in local context
>> if not shadowed by let-bindings and the like.
>
> Function parameters (or a closure's parameters and environment
> variables) are global variables in the sense that they're
> ‟instance-wide” (within the entire function or closure) and can be
> accessed in local context if not shadowed by let-bindings.
>
> But «within an entire function or closure» isn't really instance-wide?
> Well neither is «within an entire buffer».
We are not talking about "within an entire buffer". Emacs has a notion
of a "current buffer". There is no hierarchy or stack or nesting
involved: the current buffer setting swaps out variables in global
scope. It does not matter which module or buffer or context your global
variables have been defined in.
> The global environment is the outermost one. A buffer's environment is
> not.
That confusion seems to be the most compelling reason _not_ to mess with
the terminology in order not to cause additional confusion. A buffer
does not have an "environment". It has a list of global variable values
to substitute whenever it is made current. There is always exactly one
current buffer. You cannot _not_ have a current buffer:
emacs -Q --batch --eval '(message "%S" (current-buffer))'
#<buffer *scratch*>
> There's only one global environment. There can be multiple buffers and
> multiple closures, each with its own environment. ‟Buffer-local” is a
> perfectly good term for buffer-locals. Calling them ‟global” would be
> misleading, and it's good that Emacs doesn't do that.
>
> ‟Global” is the right term for globals.
And buffer-local variables _are_ buffer-local versions of _global_
variables. They are not scoped. With setq-default you are not setting
a value that is in any manner more or less global than a buffer-local
setting. It is a separate symbol slot only accessible via special
commands or when no buffer-local setting exists.
--
David Kastrup
next prev parent reply other threads:[~2015-01-24 11:03 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 2:59 Rant - Elisp terminology is deceptive Kelly Dean
2015-01-23 20:15 ` Stefan Monnier
2015-01-24 0:41 ` Kelly Dean
2015-01-24 0:48 ` Óscar Fuentes
2015-01-24 3:28 ` Stephen J. Turnbull
2015-01-24 8:51 ` Eli Zaretskii
2015-01-24 10:32 ` Kelly Dean
2015-01-24 11:26 ` Eli Zaretskii
2015-01-24 10:30 ` Kelly Dean
2015-01-24 11:03 ` David Kastrup [this message]
2015-01-24 23:24 ` Kelly Dean
2015-01-25 9:16 ` David Kastrup
2015-01-26 3:52 ` Kelly Dean
2015-01-26 8:28 ` Thien-Thi Nguyen
-- strict thread matches above, loose matches on Subject: below --
2013-05-22 3:44 [PATCH] Desktop mode saves mark-ring too verbosely Kelly Dean
2013-11-23 13:40 ` Stefan Monnier
2015-01-21 12:11 ` Kelly Dean
2015-01-21 15:04 ` Stefan Monnier
2015-01-22 5:43 ` Kelly Dean
2015-01-22 8:20 ` Ivan Shmakov
2015-01-23 13:20 ` Kelly Dean
2015-01-23 14:09 ` Ivan Shmakov
2015-01-24 3:08 ` Stephen J. Turnbull
2015-01-24 23:30 ` Elisp terminology (was: Re: [PATCH] Desktop mode saves mark-ring too verbosely) Kelly Dean
2015-01-25 9:49 ` Elisp terminology David Kastrup
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