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# Bug Tracker

ID 66 Closed (Not a Bug) probsoln 3.04 Default args are ignored

## Report

I have some problems which take no args, and a couple which do. When I try to compile with 1 required arg and a default value, pdflatex fails to compile, complaining that I need to provide a value (when using \thisproblem) or breaking the environment (using \useproblem).

RL

### MWE

\documentclass[a4paper,12pt]{article}
\usepackage[draft]{probsoln}

\begin{document}
\begin{defproblem}[1][{2}]{diffsin}
Differentiate $f(x)=\sin(#1x)$.
\begin{onlysolution}%
\begin{solution}
$f’(x) = #1\cos(#1x)$
\end{solution}
\end{onlysolution}
\end{defproblem}

\begin{enumerate}
\item \useproblem{diffsin}
%Same thing with \foreachproblem{\item\thisproblem}
\end{enumerate}
\end{document}



## Evaluation

The default arguments are only used by \thisproblem together with the package option usedefaultargs. Like this:
\documentclass[a4paper,12pt]{article}
\usepackage[usedefaultargs]{probsoln}

\begin{document}
\begin{defproblem}[1][{2}]{diffsin}
Differentiate $f(x)=\sin(#1x)$.
\begin{onlysolution}%
\begin{solution}
$f'(x) = #1\cos(#1x)$
\end{solution}
\end{onlysolution}
\end{defproblem}

\begin{enumerate}
\foreachproblem{\item\thisproblem}
\end{enumerate}
\end{document}

This is documented in the manual, but I will add a note to make it clearer.

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