Union in c++ are they feasible

Question

Can a union in C++ have a member function? How do union with data members and member functions exist if an object is created?

If I suppose yes, then are they feasible an

Answer 1

You can also make a template union :

template 
union Foo {
public:
  Foo() {}
  Foo(const T& value) : _val(value) {}

  const char* data() const {
    return _tab;
  }

  std::size_t size() const {
    return sizeof(T);
  }

  char operator[](unsigned int index) const {
      return _tab[index];
  }

private:
  T _val;
  char _tab[sizeof(T)];
}