\
@
and @
in macro namesMacro names containing @
are internal to LaTeX, and
without special treatment just don’t work in ordinary use. A nice
example of the problems caused is discussed in
\
@
in vertical mode”.
The problems users see are caused by copying bits of a class
(.cls
file) or
package (.sty
file) into a document, or by including a class or
package file into a LaTeX document by some means other than
\
documentclass
or \
usepackage
. LaTeX defines internal
commands whose names contain the character @
to
avoid clashes between its internal names and names that we would
normally use in our documents. In order that these commands may work
at all, \
documentclass
and \
usepackage
play around with the
meaning of @
.
If you’ve included a file wrongly, you solve the problem by using the correct command.
If you’re using a fragment of a package or class, you may well feel confused: books such as the first edition of the The LaTeX Companion are full of fragments of packages as examples for you to employ. This problem has been solved in the second edition, and in addition, all the examples from the Companion are now available on-line. To see the technique in practice, look at the example below, from file 2-2-7.ltx in the Companion examples directory:
\makeatletter \renewcommand\subsection{\@startsection {subsection}{2}{0mm}%name, level, indent {-\baselineskip}% beforeskip {0.5\baselineskip}% afterskip {\normalfont\normalsize\itshape}}% style \makeatother
(That example appears on page 29 of The LaTeX Companion, second edition.)
The alternative is to treat all these fragments as a package proper,
bundling them up into a .sty
file and including them with
\
usepackage
; this way you hide your LaTeX internal code somewhere
that LaTeX internal code is expected, which often looks ‘tidier’.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=atsigns