Task

Take a   Natural Number   in a given base and return the sum of its digits:

   110         sums to   1
   123410   sums to   10
   fe16       sums to   29
   f0e16     sums to   29


def digitsum = { number, radix = 10 ->
    Integer.toString(number, radix).collect { Integer.parseInt(it, radix) }.sum()
}