1 result.
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In this demo question, you can see either 2 or 3 gaps depending on the variable m, and the marking algorithm doesn't penalise for the empty third gap in cases when it is not shown.
Reason to use it: for vectors or matrices containing only numbers, one can easily use matrix entry to account for a random size of an answer. But this does not work for mathematical expressions. There we have to give each entry of the vector as a separate gap, which then becomes a problem when the size varies. This solves that problem. For this reason I've included two parts: one very simple one that just shows the phenomenon of variable number of gaps, and one which is more like why I needed it.
Note that to resolve the fact that when m=2, the point for the third gap cannot be earned, I have made it so that the student only gets 0 or all points, when all shown gaps are correctly filled in.
Note the use of Ax[m-1] in the third gap "correct answer" of part b): if you use Ax[2], then it will throw an error when m=2, as then Ax won't have the correct size. So even though the marking algorithm will ignore it, the question would still not work.
Bonus demo if you look in the variables: A way to automatically generate the correct latex code for [Math Processing Error][Math Processing Error], since it's a variable size. I would usually need that in the "Advice", i.e. solutions, rather than the question text.
