* About <DEL> character and Control character.
@ 2009-08-05 9:17 waterloo
0 siblings, 0 replies; 2+ messages in thread
From: waterloo @ 2009-08-05 9:17 UTC (permalink / raw
To: help-gnu-emacs
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I am reading Emacs Lisp Reference and can not understand the following
paragraph:
For historical reasons, Emacs treats the <DEL> character as the
control equivalent of `?':
?\^? => 127 ?\C-? => 127
As a result, it is currently not possible to represent the character
`Control-?', which is a meaningful input character under X, using
`\C-'. It is not easy to change this, as various Lisp files refer to
<DEL> in this way.
What I understand is :
?\^? = <DEL>
now we can not represent `Control-?' with `?\ " syntax.
Is it right?
What does "which is a meaningful input character under X, using
`\C-'. " mean ?
Thanks
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* Re: About <DEL> character and Control character.
[not found] <mailman.3926.1249463831.2239.help-gnu-emacs@gnu.org>
@ 2009-08-05 17:28 ` Barry Margolin
0 siblings, 0 replies; 2+ messages in thread
From: Barry Margolin @ 2009-08-05 17:28 UTC (permalink / raw
To: help-gnu-emacs
In article <mailman.3926.1249463831.2239.help-gnu-emacs@gnu.org>,
waterloo <waterloo2005@gmail.com> wrote:
> I am reading Emacs Lisp Reference and can not understand the following
> paragraph:
>
> For historical reasons, Emacs treats the <DEL> character as the
> control equivalent of `?':
>
> ?\^? => 127 ?\C-? => 127
>
> As a result, it is currently not possible to represent the character
> `Control-?', which is a meaningful input character under X, using
> `\C-'. It is not easy to change this, as various Lisp files refer to
> <DEL> in this way.
>
> What I understand is :
> ?\^? = <DEL>
> now we can not represent `Control-?' with `?\ " syntax.
>
> Is it right?
>
> What does "which is a meaningful input character under X, using
> `\C-'. " mean ?
There is no Control-? character in traditional ASCII, which is why it
was originally OK to use ^? as the way to represent DEL. But modern
windowing systems, like X, Windows, and MacOS, allow the control
modifier to be applied to any character on the keyboard. This created
the ambiguity, because now there's a real Control-?.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***
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