I am going through some undocumented code for writing about XML, where
attribute names needed to be indexed, flagged by an at-sign like @href.

The @ sign is of course already in used in makeindex data as the
"actual" (literal-to-end-of-argument) flag, used to allow font changes
like \index{keyword@\textit{keyword}}.

The code is quite clear that it is generating LaTeX \index commands
using an = sign instead of an @ sign. Oddly, this seems to be supported
by makeindex even without the /actual "="/ directive.

So there are explanatory entries like \index{@href=\texttt{@href}
(attribute)}, which end up in the .idx file as (eg)
\indexentry{href=\texttt{@href} (attribute)}{3}

With or without the /actual "="/ directive, when these are processed by
makeindex they result in a line like \item href}, 3
with a bogus closing curly brace and no @ sign.

The code was at some stage functioning and and correctly indexing.

What is the right way to index strings starting with an @ sign?
The makeindex man page implies (towards the end) that a double @@ sign
will work.

Suggestions on the back of a catalogue index card to me, please :-)

On 12/06/2023 23:43, Peter Flynn wrote:

> What is the right way to index strings starting with an @ sign?

A night's sleep and some good coffee revealed that defining
\at as an at-sign works just fine.

Peter