Creating problem-sets with answers in Latex

I want to typeset Mathematical problem-sets in Latex. My requirements are as follows:

When I type them in, I want the questions and the answers to be next to each other in the source-code so that fixing errors, etc. can be done easily.

However, when the document is typeset, I want the answers to appear in a separate "Answers" sec开发者_运维技巧tion just the way they do in textbooks.

Does anyone know of a way to do this?

Many thanks in advance!

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You are looking for deferred printing. There are packages that can handle this problem, for instance exercise. This does exactly what you're looking for.

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Define a 'question' and a 'solution' environment in your questions.tex file (say). Include questions.tex twice. The first time, include questions only. The second time, include solutions only.

\usepackage{version}

% Include questions but not solutions:
\includeversion{question}\excludeversion{solution}

% Include solutions but not questions:
%\excludeversion{question}\includeversion{solution}

\begin{document}

\begin{enumerate}

\item  % Shared question marker.
\begin{question}
Question goes here.
\end{question}
\begin{solution}
solution goes here
\end{solution}

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I developed a lot of code to do this. There are two approaches. One is you can have a function that keeps adding the answers to a variable that just gets bigger and bigger. The second is you can have function that writes to a file and then, later, reads the file into your document. Frankly, the variable method is easier, even though it seems grosser.