¬ notation for not? Ref: Add a couple cells to lisp-prettify-symbols-alist

[Drew Adams <drew.adams@oracle.com>]

> DA> E.g., ensure that "¬" does not name a symbol that has a
> DA> function or variable value.  If `¬' is already bound to some
> DA> function or variable then you probably do not want to alias
> DA> function `not' to it.
> 
> That's not really related to my question about customizations,

Irrelevant.

This is a thread about showing "¬ notation for not?" (and similar),
a thread started by that question from Clément.  My comment is about
one consideration for such a proposed feature.

My point is separate from _your_ question, but there is no reason
to fork discussion off my point off from Clément's proposed feature,
with which it is concerned.  I restored the Subject line.

> and there is no aliasing going on in any case. The user will see ¬
> in both cases, but they will be different underneath.

Yes, of course.  It is not aliasing of symbol values (function or
variable).  It is, as you say, a "visual clobbering".  Visual name
capture.

> DA> Emacs allows most characters in function and variable names.
> DA> Just because `prettify-symbols-alist' might have an entry for
> DA> a given string, that does not mean that the user wants to
> DA> clobber any existing function or variable that has that name.
> 
> It's a visual clobbering, but yeah, I know what you mean. Typically
> users will not have such functions or variables, but it would be good to
> distinguish them in a way that makes their ephemeral nature clear. Right
> now they aren't.

There is nothing inherently ephemeral in the nature of such functions
or variables.

This is not limited to any particular function or variable (e.g. `not').
Any function or variable could appear in `lisp-prettify-symbols-alist',
and it could be associated with any prettifying string.

The possibility of a visual name capture needs to be considered before
this feature is rolled out.