Are there scala-like mixins for C++?

Question

Scala Mixins

Answer 1

No, but it can be faked to varying degrees with templates:

template<typename AbsIterator> 
class RichIterator : public AbsIterator {
public:
   template<typename FuncType>
   void foreach(FuncType f) { while( hasNext() ) f( next() ); }
};

class StringIterator {
  std::string m_s;
  int i;
public:
  typedef char T;
  StringIterator() : m_s(), i(0) {} // Unfortunately need this, or 
                                    // else RichIterator
                                    // gets way more complicated
  StringIterator(const std::string &s) : m_s(s), i(0) {}
  void swap(StringIterator& other) {
     m_s.swap(other.m_s);
     std::swap(i, other.i);
  }
  void reset_str(const std::string& s) {
     StringIterator(s).swap(*this);
  }
  bool hasNext() { return i < m_s.length(); }
  char next() { return m_s[i++]; }
};

template<typename Outputable>
void println(const Outputable& o) {
   std::cout << o << std::endl;
}

int main(int argc, char **argv) {
  typedef RichIterator<StringIterator> Iter;
  Iter iter;
  iter.reset_str(argv[1]);
  iter.foreach(&println<Iter::T>);
}

To be totally honest, I've haven't tested this by compiling it, but you should get the idea.

Answer 2

Some aspects of Scala mixins can be satisfied using multiple (virtual) inheritance. Unfortunately, this often introduces more problems than it solves. Also, you can't mix and match superclasses on the fly a la:

val me = new Human with Coder with Musician

If you really, really want true mixins, you almost have to go with something like the template solution proposed in the answer by @Logan Capaldo.