Set of values, not range of values

[aasmund_kvamme]

I would like to be able to choose a variable from a set of distinct values, not only from a range.

To give an example: "You throw a dice with `n` sides. What is the probability of an even number showing?" In this example I can't choose from all numbers between 6 and 20 (for instance), but I should be able to choose from the set {6, 8, 12, 20} (for instance).

Is this possible?