[Tex/LaTex] Exercise enumeration

#enumerateexerciseslistsmacrosnumbering

In order to make it easier to write hand-in assigments, I want to create two environments Subexc and subexc, where I can write the entire exercise down before starting. Subexc is supposed to be run with an argument, specifying the enumeration format to be used (note that I am using the enumerate package). Subexc then saves the format in a variable \subExcFormat and the exercise number in a counter subExcCounter. When subexc is run afterwards, it then continues the exercise number and the format from \Subexc. An example:

\usepackage{enumerate}
\newenvironment{Subexc}[1]
{%
    \begin{enumerate}[#1]%
        \item\ignorespaces\begin{itshape}%
}{%
    \end{itshape}%
    \end{enumerate}\setcounter{subExcCounter}{\theenumi}%
    \global\let\subExcFormat#1%
    \vspace{1 mm}\par\noindent\ignorespacesafterend%
}

\newenvironment{subexc}
{%
    \begin{enumerate}[\subExcFormat]%
    \setcounter{enumi}{\thesubExcCounter}%
    \ignorespaces\item\begin{itshape}%
}
{%
    \end{itshape}%
    \end{enumerate}%
    \setcounter{subExcCounter}{\theenumi}%
    \vspace{1 mm}\par\noindent\ignorespacesafterend%
}

\begin{document}
\section*{Exercise 717}
\emph{In this exercise, we will prove the Riemann hypothesis.} %Text from exercise.

\begin{Subexc}{(a)} % Enumeration format of the form (a), (b), ...
  Prove that $8 + 7 = 15$. % exercise text.
\end{Subexc}
Blablabla %My answer

\begin{subexc} % No format; it will continue the format from the last section.
  Show that $e^{i\pi} + 1 = 0$.
\end{subexc}
Bluhbluhbluh %My answer

\begin{subexc}
   Use (a) and (b) to show the Riemann hypothesis.
\end{subexc}
Wowowow %my answer
\end{document}

However, I get the errors

Illegal parameter number in definition of \endSubexc }
Illegal parameter number in definition of \subExcFormat \end{\subexc}
Undefined control sequence \begin{subexc}
Undefined control sequence \begin{subexc}
(Warning) The counter will not be printed.

What went wrong? 🙂

Best Answer

You can't use #1 in the end part. But you can simply move the definition of \subExcFormat in the begin part. Using \theenumi is wrong: \value{enumi} is what you need (it's the cause of the warning, by the way).

\documentclass{article}
\usepackage{enumerate}
\newcounter{subExcCounter}
\newenvironment{Subexc}[1]
  {%
   \gdef\subExcFormat{#1}%
   \enumerate[#1]%
   \item\itshape
  }
  {%
   \endenumerate\setcounter{subExcCounter}{\value{enumi}}%
   \par\vspace{1 mm}\noindent\ignorespacesafterend
  }

\newenvironment{subexc}
  {%
   \expandafter\enumerate\expandafter[\subExcFormat]%
   \setcounter{enumi}{\value{subExcCounter}}%
   \item\itshape
  }
  {%
   \endenumerate
   \setcounter{subExcCounter}{\value{enumi}}%
   \par\vspace{1 mm}\noindent\ignorespacesafterend
  }

\begin{document}
\section*{Exercise 717}
\emph{In this exercise, we will prove the Riemann hypothesis.} %Text from exercise.

\begin{Subexc}{(a)} % Enumeration format of the form (a), (b), ...
  Prove that $8 + 7 = 15$. % exercise text.
\end{Subexc}
Blablabla %My answer

\begin{subexc} % No format; it will continue the format from the last section.
  Show that $e^{i\pi} + 1 = 0$.
\end{subexc}
Bluhbluhbluh %My answer

\begin{subexc}
   Use (a) and (b) to show the Riemann hypothesis.
\end{subexc}
Wowowow %my answer
\end{document}

I removed also useless \ignorespaces commands, \begin{itshape} and \end{itshape}. I remain dubious about

   \par\vspace{1 mm}\noindent\ignorespacesafterend

that seems superfluous; just avoid a blank line if you don't want a new paragraph. Note also \par\vspace{1mm} rather than the inverse.

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