A custom interval parser and previewer is needed

[JoshuaCapel]

Currently questions are given to student where the answer is an interval (e.g. [0,infinity)), but students are unable to preview this to confirm their input is as expected.

A library should be written to:

1. Parse the student input into a canonical form for grading.
2. Preview the input response and report if the the preview has failed (potentially with a reason).

This input is likely to be very limited in scope (for example, we may want to assume that only a single comma will appear in the input to help split the strings). For this reason it will be separate from the general previewing library.

Helpful option features would be:

• The ability to specify a language (e.g. Maple, Matlab, Numbas).
• The ability to allow for typographical errors (e.g., in high-stakes non repeatable assessments)
• The ability to pass functions to be run as pre-processing or post-processing on the response.