Adjust to the moving target called the C++ standard. Apparently nowadays it's not allowed to define an explicit copy constructor but not an assignment operator. Consequently, defining the explicit copy constructor in terms of the implicit/automatic assignment operator for general convenience no longer works. Add assignment operators. Caution: not tested with the IBM compiler, but there's no particular reason it shouldn't work.

grammar
  -> '0-9':d, !printf("%d\n", d);, '0-9':i = 10*d + 1;
  -> 'a-f':d, !printf("%d\n", d);, '0-9'