Errors not allowing compiling [closed]

Question

I'm new to Latex, but have been making a study guide for my class which has gotten very large. I changed one small thing, I believe I changed a section name, and now I get this error that I cannot for the life of me fix to allow for compiling again. Does anyone know what this error means and where it could be in my document to fix? Thanks!

~<inserted text> 
                \par 
l.36 ... {section}{\includepdf }{253}{section*.37}
                                                  %
I've run across a `}' that doesn't seem to match anything.
For example, `\def\a#1{...}' and `\a}' would produce
this error. If you simply proceed now, the `\par' that
I've just inserted will cause me to report a runaway
argument that might be the root of the problem. But if
your `}' was spurious, just type `2' and it will go away.

Runaway argument?~

Answer 1

Here is an other illustration of the 50:50 strategy I suggested. It's a simple example, and your trouble will probably on a similar level, in a comparable place.

The keys here are:

• follow a systematic process
• until the point, where you know where to look for what
• correct it and continue

Needless (?) to say, you should do the following on a copy of your files ..., just in case ...

Iteration 1 - knowing nothing

Let's assume you have a file like this, and let's pretend we don't spot the error right away.

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} }

\begin{document}
 \section{Just a section}
 \lipsum[1]
 
 \includegraphics[scale=.3]{example-image} 
 
 \section{\strange{hello world} }
 \lipsum[5]
 
\end{document}

A compile yields

Though it hints to line 14, we might not be able to understand the problem, as there is no image at line 14 ...:

! LaTeX Error: File `example-images' not found.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.14 \section{\strange{hello world} }
I could not locate the file with any of these extensions: ...

Iteration 2 - where is it, roughly? (split 50:50)

Let's continue pretending we are blind enough to overlook the obvious. Let's comment out the lower part, which compiles:

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} }

\begin{document}
 \section{Just a section}
 \lipsum[1]
 
% \includegraphics[scale=.3]{example-image} 
% 
% \section{\strange{hello world} }
% \lipsum[5]

Is the problem here? Let's check the opposite, i.e. "the other 50%":

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} }

\begin{document}
% \section{Just a section}
% \lipsum[1]
 
 \includegraphics[scale=.3]{example-image} 
 
 \section{\strange{hello world} }
 \lipsum[5]
 
\end{document}

This fails, so the problem must be somewhere here.

Iteration 3 - closer look at lower half (split 50:50)

With the previous hint in mind, and line 14 back again, let's try this half (of the previous half):

Compiles:

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} }

\begin{document}
% \section{Just a section}
% \lipsum[1]
 
 \includegraphics[scale=.3]{example-image} 
 
% \section{\strange{hello world} }
 \lipsum[5]
 
\end{document}

Proof: dosen't compile

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} }

\begin{document}
% \section{Just a section}
% \lipsum[1]
 
% \includegraphics[scale=.3]{example-image} 
 
 \section{\strange{hello world} }
% \lipsum[5]
 
\end{document}

Iteration 4 - what's in a line? (split 50:50)

Now, we no longer can run away from the fact that this line bears something strange: \section{\strange{hello world} }

How to narrow it down? Make it discardeble: 50:50 on the next lower level.

This fails (with the rest as above)

 \section{
    \strange{hello world} 
 }

while this compiles:

 \section{
%   \strange{hello world} 
 }

Iteration 5 - time of focused analysis and enlightment

Ok, let's have a close look at this strange macro. Who defined it? Me myself? Ok:

\newcommand\strange[0]{\includegraphics[scale=.3]{example-images} 

Either repeating reformating and compile as with the section, or rereading the error message again, sooner or later you'll wonder:

• who defined example-images ?
• answer: nobody
• it's true, that package graphicx provides an example-image (at least)
• but it doesn't provide example-images

So, was it a typo?

Proof

Ok, let's try the changed filename ... and it compiles.

\documentclass[10pt,a4paper]{article}
\usepackage{lipsum}
\usepackage{graphicx}
\newcommand\strange[0]{\includegraphics[scale=.3]{example-image} }

\begin{document}
 \section{Just a section}
 \lipsum[1]
 
 \includegraphics[scale=.3]{example-image} 
 
 \section{
    \strange{hello world} 
 }
 \lipsum[5]
 
\end{document}