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Re: Introducing thread-safe Tramp

From: Howard Melman
Subject: Re: Introducing thread-safe Tramp
Date: Mon, 6 Aug 2018 11:52:12 -0400

> On Aug 6, 2018, at 10:52 AM, Drew Adams <address@hidden> wrote:
>>> My sense is that the proposed C-x & is a prefix, because it
>>> is used before another key sequence. It is not an argument
>>> because it doesn't affect the functions' argument list the
>>> way C-u does.
>>> Maybe the term should be "prefix sequence"?
>> I like this proposal. "Prefix key sequence" would be more precise, but
>> it doesn't read fluid. If there isn't any objection over the next week,
>> I'll apply your wording.
> Please don't.
> This is _not_ a prefix key. A key is a key sequence. A prefix key is a key 
> sequence that is a prefix of a larger key sequence. But in Emacs a prefix key 
> also has the specific meaning of a key sequence that is bound to a keymap. 
> `C-x &' is not bound to a keymap, and is thus not a prefix key (sequence).
> Until and unless we really do decide to baptize this and document it, please 
> just what RMS suggested: don't call it anything. Certainly please do not call 
> it just a "prefix" or a "prefix key (sequence)".

Having reread the Keys section of the Emacs manual I see your objection. Since 
"key" is short for "key sequence", then indeed it's not a "prefix key 
(sequence)" or a "(prefix key) sequence". My intention was to read it as 
"prefix (key sequence)", as something that comes before a key sequence, though 
clearly the ambiguity is an issue.

> What is it a prefix of? A prefix is part of what it is a prefix of.

It's a prefix of a key sequence, and it is a key sequence itself ("a sequence 
of one or more input events is is meaningful as a unit"). It's kind of a 
"complete key" ("a key sequence [that] invokes a command"), though it's a 
"complete key" that needs more. Maybe it's a "semi-complete key" as something 
between the existing terms "complete key" and "prefix key" and the full 
sequence C-x & C-x C-f is still a complete key sequence.

As you pointed out, technically C-u isn't a prefix key because it calls the 
command universal-argument, maybe it also is a semi-complete key. (Though 
clearly it would always be more useful to describe C-u as beginning a prefix 

>>> Wasn't there are a proposal at one point to do something
>>> similar for C-x 4 and C-x 5 so that there didn't have to be
>>> -other-window and -other-frame variants of so many
>>> commands?
>> I'm not aware of such a proposal (which only means that my memory is
>> bad), but it makes sense.
> I believe he's thinking of Stefan's wish to have prefix keys `C-x 4' and `C-x 
> 5' work automatically, without defining separate other-window and other-frame 
> commands. That's something completely different. Let's please not let this 
> thread wander farther than it already has.

Yes, that's what I was thinking of. I'm not sure if there was a proposed 
implementation or if it was similar to this one, but the usage struck me as 
similar. Since this is a proposal to name a new kind of thing, it didn't feel 
like wandering to to test it against other similar kinds of proposals to see if 
it would cover them as well.


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