[Tex/LaTex] How to use figure inside a exercise environment

environmentsexercisesfloats

Trying to use figure inside an Exercise environment (exercise.sty) gives me "LaTeX Error: Not in outer par mode."

Example:

\documentclass{article}

\usepackage[]{exercise}
\begin{document}

\begin{Exercise}[title={foo}, label=ex1]
A tough question.
\end{Exercise}

\begin{Answer}[ref={ex1}]
A smart answer.

\begin{figure}[htp]
   \centering
   \includegraphics[totalheight=0.2\textheight]{couetteFlowFig1.png}
   \label{fig:ex1}
\end{figure}
\end{Answer}

\end{document}

I see in Is it possible to use the figure environment with the standalone package? that there was a similar problem with a different package, and that limitation in the package was eventually handled. It appears the same limitation exists in the exercise environment. Is there a work around that allows for inclusion of a figure with that package, or a different way of including a figure when using this package?

Best Answer

There is no requirement to place an image (using \includegraphics, say) inside a figure environment. The figure environment is merely a floating placeholder. So, you can just put your image inside a center environment to centre it on the page, and even add a caption using \captionof from the caption package.

enter image description here

\documentclass{article}
\usepackage{caption}% http://ctan.org/pkg/caption
\usepackage{exercise}% http://ctan.org/pkg/exercise
\begin{document}

\begin{Exercise}[title={foo}, label=ex1]
A tough question.
\end{Exercise}

\begin{Answer}[ref={ex1}]
A smart answer.

\begin{center}
  %\includegraphics[totalheight=0.2\textheight]{couetteFlowFig1.png}
  \rule{150pt}{100pt} \par
  \captionof{figure}{This is a figure caption.}
  \label{fig:ex1}
\end{center}
\end{Answer}

\end{document}

In the above example, I've replaced the image with a rectangular block to simulate the image, but it will work with \includegraphics as well (for which you will require \usepackage{graphicx} - the graphicx package).

The problem originates from inserting figure inside Exercise. Or, more generally, a float inside a non-floating (or restrictive) environment. Therefore, removing the floating environment enables the compilation to succeed.

Related Solutions

[Tex/LaTex] An inline exercise environment

Here is an implementation that provides a \exinline command, taking a label argument to produce the relevant text.

Sample output

\documentclass{article}

\usepackage{amsthm}

\newtheorem{theorem}{Theorem}[section]
\newtheorem{exercise}[theorem]{Exercise}

\newcommand{\exinline}[1]{(\refstepcounter{theorem}Exercise~\thetheorem\label{#1})}

\begin{document}

\section{Euler's Theorem}

Some text.

\begin{theorem}[Euler]
  \label{thm:Euler}
  This is Euler's theorem.
\end{theorem}

\begin{proof}
  The proof of this theorem is left as an exercise \exinline{ex:Euler}.
\end{proof}

\begin{exercise}
  \label{ex:extra}
  Reformulate the theorem.
\end{exercise}

Here is the solution to Exercise~\ref{ex:Euler}.  By\dots

Note that Exercise~\ref{ex:extra} requires you to provide another formulation
of Theorem~\ref{thm:Euler}.

\end{document}

Note in this example Exercises and Theorems share the same counter. If that is not the case, you need to replace the theorem counter in definition with the appropriate counter, and change \thetheorem correspondingly. E.g. if exercises have their own number, declared via \newtheorem{exercise}{Exercise}[section], the command definition should read

\newcommand{\exinline}[1]{(\refstepcounter{exercise}Exercise~\theexercise\label{#1})}

If you are using cleveref for references then a small modification is needed to the refstepcounter command so \cref picks up the correct name.

\documentclass{article}

\usepackage{amsthm}
\usepackage[capitalize]{cleveref}

\newtheorem{theorem}{Theorem}[section]
\newtheorem{exercise}[theorem]{Exercise}

\newcommand{\exinline}[1]{(\refstepcounter[exercise]{theorem}Exercise~\thetheorem\label{#1})}

\begin{document}

\section{Euler's Theorem}

Some text.

\begin{theorem}[Euler]
  \label{thm:Euler}
  This is Euler's theorem.
\end{theorem}

\begin{proof}
  The proof of this theorem is left as an exercise \exinline{ex:Euler}.
\end{proof}

\begin{exercise}
  \label{ex:extra}
  Reformulate the theorem.
\end{exercise}

Here is the solution to \cref{ex:Euler}.  By\dots

Note that \cref{ex:extra} requires you to provide another formulation
of \cref{thm:Euler}.

\end{document}

This produces the same output as the first example, with cleveref correctly providing the names.

[Tex/LaTex] How to use package ‘answers’ with one’s own solution environment

From my Update I tried to improve the code. I realized that Soln needs to have three arguments and I made them all formal/required arguments so that answers can work with them (this part originally failed). I didn't need to use hyperlink specifically (the links turned out correctly). I'll convert this MWE into the original document and see whether everything still works (I'll report back if not). Feel free to comment on possible improvements of the code.

\documentclass{scrreprt}
\usepackage[american]{babel}
\usepackage{mathtools}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{etoolbox}
\usepackage{marginnote}
\usepackage{answers}
\usepackage{hyperref}

\newcounter{counter}
\numberwithin{counter}{section}

\newenvironment{exercise}[2]{\refstepcounter{counter}\par% #1 = header; #2 = label
  \trivlist
  \labelsep 0pt
  \def\mysollabel{#2}
  \preto\mysollabel{sol:}
  \def\myexlabel{#2}
  \preto\myexlabel{ex:}
\item[\hskip\labelsep\sffamily\bfseries Exercise~\thecounter~(#1)]\label{\myexlabel}% this '\label' refers to the exercise
  \marginnote{Solution~p.~\pageref{\mysollabel}}%
  \ignorespaces%
}{%
  \endtrivlist
}

\Opensolutionfile{solutions}
\Newassociation{solution}{Soln}{solutions}

\begin{document}
\section{Exercises Section 1}
\begin{Filesave}{solutions}
  \clearpage
  \section{Solutions Section 1}
\end{Filesave}

\newcommand*{\headerOne}{Header 1}
\begin{exercise}{\headerOne}{ex:1:label}\\
  First exercise
  \begin{solution}{\headerOne}{ex:1:label}\\
    First solution.
  \end{solution}
\end{exercise}

\clearpage
\section{Exercises Section 2}
\begin{Filesave}{solutions}
  \clearpage
  \section{Solutions Section 2}
\end{Filesave}

\newcommand*{\headerTwo}{Header 2}
\begin{exercise}{\headerTwo}{ex:2:label}
  \begin{enumerate}
  \item Part 1
  \item Part 2
  \end{enumerate}
  \begin{solution}{\headerTwo}{ex:2:label}
    \begin{enumerate}
    \item Solution Part 1
    \item Solution Part 2
    \end{enumerate}
  \end{solution}
\end{exercise}

\Closesolutionfile{solutions}

\renewenvironment{Soln}[3]{% #1 = label (from 'answers'; #2 = header; #3 = label
  \pushQED{\qed}
  \trivlist
  \labelsep 0pt
  \def\myexlabel{#3}
  \preto\myexlabel{ex:}
  \def\mysollabel{#3}
  \preto\mysollabel{sol:}
\item[\hskip\labelsep\sffamily\bfseries Solution~#1~(#2)]\label{\mysollabel}%
    \marginnote{Exercise~p.~\pageref{\myexlabel}}%
    \ignorespaces%
}{%
  \popQED\endtrivlist
}

\clearpage
\IfFileExists{solutions.tex}{\input{solutions.tex}}{}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] An inline exercise environment

[Tex/LaTex] How to use package ‘answers’ with one’s own solution environment

Related Question