>> "Stefan" == Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> No, I mean the thing that visually replaces α with an actual
>> α character (and converts it back when you save).

   > Did I write the above?  Sorry, the first α should have been "\alpha".
   > And I was just referring to the X-Symbol feature:

   > AFAIK, one of one of X-Symbol's features is to shows you "nice symbols
   > and such", such as → ⊢ α, in place of the corresponding TeX code (such
   > as \to, \vdash, \alpha).  It does it in a way which is fairly intrusive,
   > replacing the \to, \vdash, \alpha text itself in the buffer (and
   > replacing it back when saving).

   > And I was pointing out that nowadays it would be a lot more natural to
   > do that via prettify-symbols-mode which would be more efficient and
   > wouldn't requiring changing the buffer's content (so, no risk of
   > messing up the file's content either).

You are right, also I find the symbols provided my the functionality you
mentioned quite ugly compared to the one presented by x-symbol, a bit
like comparing a math documented generated by (La)TeX or say by an IBM
from then seventies.....



   > I know that, but what does it have to do with X-Symbol?

When x-symbol was introduced a bit more than 20 years ago it was
revolutionary.

   > More to the point: Emacs's built-in LaTeX mode already displays those
   > above "_k" and "^l" as sub- and superscripts (and has been doing it for
   > many years now).

   > So, what did X-Symbol do with super/subscript that isn't covered by this?


Well it does not display the ugly _ (while in x-symbols the _ or ^ are
omitted when the indices are displayed)[1]

Another important feature, which I have not seen so far by other
packages concerns: Graphics! Pdf, jpg gif

For example 
if you have 
\includegraphics{function.jpg}
in your latex file, then 
x-symbol with represents graphic file inline (in the same buffer) via
imagemagick

Uwe 

Footnotes:
[1]  and the functionality you describe does not work unfortunately in
     Xemacs, which is irrelevant for this list, but worth to mention.