# Adding section to appendix causes a compile error

## Background

Include multiple appendixes in a book. (Using KOMA Script v2.)

## Problem

I have isolated the problem and created a minimal example to demonstrate the issue:

The only difference (according to gVim's diff tool) between good.lyx and bad.lyx are the following lines:

\begin_layout Subsection
jasper.php
\end_layout

\begin_layout Standard
TODO
\end_layout


Loading good.lyx into LyX works as expected: a PDF can be created. Loading bad.lyx into LyX does not work as expected. The following error results:

Missing number, treated as zero.

\end{document}

A number should have been here; I inserted '0'. (If you can't figure out why I needed to see a number, look up weird error' in the index to The TeXbook.)

## Questions

• Why does typing one more subsection cause an error?
• How can the error be resolved so that any number of sections and subsections can be added to the appendix?

Thank you!

-
I don't like files being stored externally on file hosting services which open browser windows with promotionial content when I try to open your files to debug. – Stefan Kottwitz Dec 8 '10 at 2:35
@Stefan: Sorry about that; it was the first free file sharing host I found. – Dave Jarvis Dec 8 '10 at 3:39
not a big problem :-) there may be free and opensource pastebin services too. But the best is always to reduce to a handy example. ;-) LyX files are also just in text format and could be posted. – Stefan Kottwitz Dec 8 '10 at 13:04
@Stefan: Will find a pastebin for next time; I just cannot bear to paste huge code snippets. (Now if there was a way to "fold" or close the snippet, that would be altogether different.) – Dave Jarvis Dec 8 '10 at 14:30
I would like to see a code folding feature, unfortunately it has been declined: meta.stackexchange.com/questions/5199/… – Stefan Kottwitz Dec 8 '10 at 15:24

What does this harmless subsection command? It starts a new page! And this page has a different page style. The first page has page style plain because it's the beginning of a chapter, but the next page has scrheadings style. There we may search the problem.

\rehead{\textsc{\ChapterTitle \ChapterNumberIfNeededEven}}
...
\def\ChapterNumberIfNeededEven{%
\ifnum 0<\thechapter{} $\star$ \chaptername{} \thechapter{} \fi
}
\def\ChapterNumberIfNeededOdd{%
\ifnum 0<\thechapter{} \chaptername{} \thechapter{} $\star$ \fi
}


Don't compare a number 0 with \thechapter - in your appendix \thechapter is "A" ! Instead, something like

 \ifnum\value{chapter}=0 ...
`

could work.

On a plain chapter starting page that error could not occur.

-
Thank you. – Dave Jarvis Dec 8 '10 at 3:45
Most compiled languages tell you the line or the expression (macro) that caused the error. I suppose that's the only thing about (La)TeX I dislike: when an error happens you have to make inferences and re-examine everything. Since LyX was not creating the page (due to the error), I could not see that it was a new page causing the problem. And I had long since forgotten about the code I wrote to change the chapter heading ("set it and forget it"). Anyway, thanks again. – Dave Jarvis Dec 8 '10 at 14:27