I'm familiar with the concept of using common code for multiple constructors. It's not really the same thing, but it's used for the same purpose; in fact, it's probably more general. It's difficult to apply to C++ because initialization semantics and syntax are not conducive. However, using an intermediate base class does the trick here.

To do the same thing as these declared initial values, you need to derive a new type for each member in question, to arrange it so its default value is exactly what you wanted.

—John