Re: Fwd: C-[ is undefined

[Ben Bacarisse]

Michael Brand <michael.ch.brand@gmail.com> writes:

> Hi Ben
>
> On Thu, Jul 26, 2018 at 6:38 AM, Ben Bacarisse <ben.lists@bsb.me.uk> wrote:
>> The following message is a courtesy copy of an article
>> that has been posted to gnu.emacs.help as well.
>>
>> Michael Brand <michael.ch.brand@gmail.com> writes:
>>
>>> There seems to be no answer yet but I am still stuck and would
>>> appreciate any help to get further.
>>
>> I'll make a remark, not sure if it will help...
>>
>>> ---------- Forwarded message ----------
>>> From: Michael Brand <michael.ch.brand@gmail.com>
>>> Date: Sat, Jul 7, 2018 at 1:52 PM
>>> Subject: C-[ is undefined
>>> To: help-gnu-emacs@gnu.org
>>>
>>> Short story: ~C-x @ c [~ results in "C-[ is undefined" but I expected
>>> it to be the Meta prefix like in for example ~C-[ t~ for ~M-t~.
>>
>> I would expect C-x @ c [ to be the same as C-[
>
> Did you try? For me it is not the same which is what I wanted to say
> in the first place.

Yes, I tried it, but my interpretation of the result ("C-[" is
undefined) was that C-x @ c [ was a way to generate a "key" that could
not otherwise be typed.

That's kind of what happens.  For example, you can bind C-[ this way and
still use C-[ to get the ESC- prefix.

However, that seems like an unlikely explanation!  It is probably
something to do with translated key sequences.  ESC and C-[ are not
exactly the same, but I am not expert enough to explain the way in which
they differ.

>> and not anything to do with a Meta modifier.
>
> What do you mean by this when ~C-[ t~ is the same as ~M-t~? I expected
> that ~C-x @ c [ t~ to be the same as ~C-[ t~ which is the same as
> ~M-t~.

Ah, yes, I see.  C-x @ c [ is obviously not identical to C-[ in some
subtle way.  Or, more likely, C-[ is special in some way.  When you list
the key bindings (C-h b) there is no entry for C-[ but ESC appears twice
-- once as a prefix and then again in the place you'd expect C-[ to
appear.

Anyway, the long and the short of it is that I can't help which is a
shame since I now actually understand the issue you are having!

-- 
Ben.