Extending enums

There might come a scenario where you want to include an enum into a another one where the first one is a subset.

#include
struct enum_a {
     enum constant {
         a, b, c, d,
         end_of_enum_a = d
     };
};
struct enum_b : public enum_a {
     enum constant {
         e = end_of_enum_a + 1,
         f, g, h
     };
};
int main() {
     std::printf("enum_a: a(%d), b(%d), c(%d), d(%d)\n",
         enum_b::a, enum_b::b, enum_b::c, enum_b::d);
     std::printf("enum_b: e(%d), f(%d), g(%d), h(%d)\n",
         enum_b::e, enum_b::f, enum_b::g, enum_b::h);
     return 0;
}

Inheritance to the rescue. :-)