As a non-standard extension to C++, common compilers allow the use of classes as anonymous members.
struct Example {
struct {
int inner_b;
};
int outer_b;
//The anonymous struct's members are accessed as if members of the parent struct
Example() : inner_b(2), outer_b(4) {
inner_b = outer_b + 2;
}
};
Example ex;
//The same holds true for external code referencing the struct
ex.inner_b -= ex.outer_b;