Re: Feature request: multilevel indexing for TeX

[Gavin Smith]

On Mon, Mar 04, 2019 at 12:34:42AM -0700, address@hidden wrote:
> No. As per the mail you discovered, Karl just said "make it work with both"
> so I did. But we're five years later, let's just make the change, please.

Made in commit 2405caa.  Provided the latest revision of texi2dvi is 
being used, old sorted index files should be painlessly updated to use 
the @ sign.  It is quite a complicated issue, and there is a significant 
risk of breakage.  Testing with various combinations of files and programs
would be useful.

Using @ as the escape character does appear to simplify matters a lot 
and reduce the need for special handling of backslashes.  Some more 
simplication of texinfo.tex might be possible around this area.

texindex should continue to recognize \ as the escape character for
compatibility with old versions of texinfo.tex.  Even if a new version is 
installed on a system, it is possible that an old version will be used 
instead if it is bundled along with a Texinfo file in the same 
directory, e.g. in old software releases.  I can't see that this would 
ever change.

> > > Or we could go with keywords, to ensure that the user gets what they
> > > wanted:
> > >
> > >   @cindex espresso makers @see{coffee makers}
> > >   @cindex coffee @seealso{instant coffee}
> >
> > I think keywords are the way to go here.
> 
> All sounds good.  I will assume that if the second entry doesn't
> have a number in it that it's a "see" or "see also" entry and
> treat it approriately.
> 
> Hmm. Do we ever get roman numerals in the number field of an entry?

I tested it and yes, this can happen.  With the input

\input texinfo.tex    @c -*-texinfo-*-
@setfilename test.info

@cindex foo
@contents

@node Command and Variable Index
@unnumbered Command and Variable Index

This is an alphabetical list of all the @@-commands, assorted Emacs Lisp
functions, and several variables.  To make the list easier to use, the
commands are listed without their preceding @samp{@@}.


@printindex cp


@bye

at the end, test.cp contained:

@entry{foo}{i}{foo}

Is the "see also" feature something that anybody 
wants or is it just theoretical?

Even if it is theoretical, it is probably a good idea to think about it 
now, as it may be hard to add the feature later in a nice way if it is 
not well-thought out now.  It occurs to me that we have the option of 
changing the index file format quite a lot, as we have already made an 
incompatible change (changing \ to @).