Your bubble sort in macro is clever, but…

[daniel-pfeiffer]

it doesn’t solve the problem, which you say was to sort numbers. You took the liberty to reduce that to a tiny subproblem of sorting only digits. I was disappointed, because just now I too need compile time sorting.

You can call const {} and const functions in a macro^*). Alas sorting is not const. I’m considering rolling my own, but again mem::swap is not stabilised in const. But with a <T: Copy> generic parameter I can (a, b) = (b, a).

^*) I did this recently, implementing a compile time number parser macro mostly as functions.