Re: Feature request: multilevel indexing for TeX

[Gavin Smith]

On 3/3/19, address@hidden <address@hidden> wrote:
> A few questions.
>
> 1. texindex.awk has provision for both \ and @ to be the command character
> (\entry vs. @entry). Do we still need that? Or will it always be backslash?

I think it could change to @ at some point. The toc and aux files do
use @ as the escape character, so it would be more consistent to use
@.

There is this comment in the code:

  % Index files are almost Texinfo source, but we use \ as the escape
  % character.  It would be better to use @, but that's too big a change
  % to make right now.

I don't know when it got added, but it was present in Texinfo 3.9 from
1996. (It wasn't in Texinfo 3.1, and I don't have copies of anything
in between (does anybody know where I could get them?).)

For the toc files at least, this changed on 2005-02-19 according to
the ChangeLog (formerly it was the backslash). In the past, the aux
file used the apostrophe (') as the escape character - that changed on
2003-01-24.

I went looking for past emails about the reasoning behind the choices
of escape char but found nothing. Did you look into this when you
wrote texindex?

> 2. What do we wish to do about "see" and "see also"? I have a thought...
>
> With respect to output from texindex.awk, I suggest that each macro
> allow empty page number arguments.  Thus
>
>       @cindex coffee makers @subentry electic
>       @cindex coffee makers @subentry gerbel-driven
>
> with no
>
>       @cindex coffee makers
>
> would yield
>
>       \entry {coffee makers}{}
>       \secondary {electric}{3, 12}
>       \secondary {gerbel-driven}{9, 42}
>
> and similar for \secondary if there are following \tertiary entries.

I'd have to check if this was easy to implement in TeX, but it is
quite likely possible. (The formatting of index entries is already
quite complicated with dealing with line breaks inside index text
and/or the list of page numbers.) I see why you would want this:
otherwise, we would need two versions of \secondary.