创建一个遍历2个容器的迭代器

我需要一个像以下一样的“容器”.它有2个子容器,称为A和B,我需要能够迭代A,只有B,A和B组合.我不想为冗余数据使用额外的空间,所以我想让我自己的迭代器迭代A和B组合.制作自己的迭代器最简单的方法是什么？或者,另一种方法是什么？

编辑最终,我不认为这是好的设计.我重新设计了整个班级的heirarchy. 1用于重构.但是,我确实充分地解决了这个问题.这是我所做的缩写版本,仅供参考;它使用boost :: filter_iterator.设T为容器中的类型.

enum Flag
{
    A_flag,B_flag
};

class T_proxy
{
public:
    T_proxy(const T& t,Flag f) : t_(t),flag_(f) {}
    operator T() const {return t_;}
    Flag flag() const {return flag_;}
    class Compare
    {
    public:
        Compare(Flag f) : matchFlag_(f) {}
        operator() (const T_proxy& tp) {return tp.flag() == matchFlag_;}
    private:
        Flag matchFlag_;
    };
private:
    T t_;
    Flag flag_;
};

class AB_list
{
public:
    typedef T_proxy::Compare Compare;
    typedef vector<T_proxy>::iterator iterator;
    typedef boost::filter_iterator<Compare,iterator> sub_iterator;
    void insert(const T& val,Flag f) {data_.insert(T_proxy(val,f));}
    // other methods...

    // whole sequence
    iterator begin() {return data_.begin();}
    iterator end() {return data_.end();}

    // just A
    sub_iterator begin_A() {return sub_iterator(Compare(A_flag),begin(),end());
    sub_iterator end_A() {return sub_iterator(Compare(A_flag),end(),end());

    // just B is basically the same
private:
    vector<T_proxy> data_;
};


// usage
AB_list mylist;
mylist.insert(T(),A_flag);
for (AB_list::sub_iterator it = mylist.begin_A(); it != mylist.end_A(); ++it)
{
    T temp = *it; // T_proxy is convertible to T
    cout << temp;
}

typedef multi_index_container<
  Container,indexed_by<
    sequenced<>,//gives you a list like interface
    ordered_unique<Container,std::string,&Container::a_value>,//gives you a lookup by name like map
    ordered_unique<Container,&Container::b_value> //gives you a lookup by name like map
  >
> container;