Typesetting braces to the index

Question

I am trying to put { in index using xindy as my index processor and xelatex as the typesetting format:

\documentclass{article}
\usepackage{makeidx}
\makeindex
\usepackage{fontspec}
\begin{document}
This is a test
\index{\texttt{\{}}
\printindex
\end{document}

However, I get the following error:

Runaway argument?
{\texttt{\{}} \printindex \end{document} 
! File ended while scanning use of \@wrindex.
<inserted text> 
                \par 
<*> test.tex

What's wrong and how do I fix it?

Answer 1

There are two issues:

• if you want to format index entry with \texttt, \textbf or similar command, use index entry in the form:

  \index{word@\textbf{word}

• for index entries which are not alphanumeric, you should provide sort key. so if you want to sort left brace as braceleft, use this:

  \index{braceleft@\texttt{\textbraceleft}}

this will create following .ind file after running

 xindy -L english -C utf8 -M texindy filename.idx

\begin{theindex}
  \providecommand*\lettergroupDefault[1]{}
  \providecommand*\lettergroup[1]{%
      \par\textbf{#1}\par
      \nopagebreak
  }

  \lettergroup{B}
  \item \texttt{\textbraceleft}, 1

\end{theindex}

if you don't want to sort it under some letter, use

\index{\relax@\texttt{\textbraceleft}}

this produces:

\begin{theindex}
  \providecommand*\lettergroupDefault[1]{}
  \providecommand*\lettergroup[1]{%
      \par\textbf{#1}\par
      \nopagebreak
  }

  \lettergroupDefault{default}
  \item \texttt{\textbraceleft}, 1

\end{theindex}

Answer 2

I can do this as

\documentclass{article}
\usepackage{makeidx}
\makeindex
\usepackage{fontspec}
\begin{document}
This is a test
\index{\texttt{\textbraceleft}}
\printindex
\end{document}

But this time xindy gives the following error message:

ERROR: CHAR: index 0 should be less than the length of the string

or alternatively as

\documentclass{article}
\usepackage{makeidx}
\makeindex
\usepackage{fontspec}
\begin{document}
This is a test
\index{\texttt{\char"007B}}
\printindex
\end{document}

but then again, xindy converts \char"007B (in the .idx file) to \char007B (in the .ind file) perhaps because " has special meaning for xindy and xindy simply ignores it.

Alternative, I can do it as

\documentclass{article}
\usepackage{makeidx}
\makeindex
\usepackage{fontspec}
\chardef\mylb="007B
\begin{document}
This is a test
\index{\texttt{\mylb}}
\printindex
\end{document}

But this time xindy gives the following error message:

ERROR: CHAR: index 0 should be less than the length of the string

Answer 3

I found the following solution by Heiko Oberdiek:

\documentclass{article}
\usepackage{makeidx}
\makeindex
\begingroup
  \lccode`0=`\{
  \lccode`1=`\}
\lowercase{%
  \endgroup
  \newcommand\BraceLeft{0}%
  \newcommand\BraceRight{1}%
}
\newcommand*{\Index}[1]{%
  \index{#1}%
}

\begin{document}
foo\Index{"\BraceLeft @\string\textbraceleft}
\printindex
\end{document}

I do not understand German and I just copied his TeX code. If you speak German, please edit my answer and add some details.