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Interval
Consider the case that the answer to a problem is an interval.
The solution is defined by a left boundary ([ for closed and ] for open), two semicolon separated numbers or variables,
and a right boundary (] for closed or [ for open).
Here is an example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15  \begin{problem}
\begin{question}
\text{Write down the Interval from 1 to 3:}
\explanation{Test test Test}
\type{input.interval}
\field{rational}
\begin{answer}
\text{ A = }
\solution{[1;3]} % or ] for open type, the boundaries should be separated by ";"
\end{answer}
\end{question}
\end{problem}

There is the optional TeX command \allowIntervalUnionsForInput[<boolean, default: true>]
with which you can enable
the option that the student's answer can be given by the union of multiple intervals.
1 2 3 4 5  \begin{answer}
\text{input.interval: $[1;4) = $}
\allowIntervalUnionsForInput
\solution{[1;4)}
\end{answer}

Furthermore as an author you can give the correct solution as an union of multiple disjoint intervals by separating
them with a comma, an example: \solution{(infinity;2],[3;infinity)}
Be aware that this is only possible if the optional command \allowIntervalUnionsForInput
is used.
More Examples