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


: sum-digits ( base n -- sum ) 0 swap [ dup zero? ] [ pick /mod swapd + swap ] until drop nip ;
 
{ 10 10 16 16 } { 1 1234 0xfe 0xf0e } [ sum-digits ] 2each