使用C++0x变长参数模板实现元组

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最近有空研究了一下C++0x相关的问题，并且在GCC4.6下用变长参数模板实现元组。

 

template
struct MyTuple;

template<> struct MyTuple<> {};

template
struct ElementType;

template
struct MyTuple
{
    MyTuple(Head h, Tail... t)
        : tail(t...)
        , head(h)
    {
    }
    MyTuple(const MyTuple& t)
        : tail(t.tail)
        , head(t.head)
    {
    }
    MyTuple(MyTuple&& t)
        : tail(t.tail)
        , head(t.head)
    {
    }

    MyTuple tail;
    Head head;

    typedef Head HeadType;
    typedef MyTuple TailType;
};

//获取元组指定元素的值
template 
struct get_class {
    template 
    static typename ElementType >::type& get(MyTuple& t )
    {
         return get_class::get(t.tail);
    }

    template 
    static const typename ElementType >::type& get(const MyTuple& t )
    {
         return get_class::get(t.tail);
    }
};

template <>
struct get_class<0> {

    template 
    static typename MyTuple::HeadType& get(MyTuple& t )
    {
         return t.head;
    }

    template 
    static const typename MyTuple::HeadType& get(const MyTuple& t )
    {
         return t.head;
    }
};

//推导元组指定元素的类型
template
struct ElementType
{
private:
  typedef typename T::TailType Next;
public:
  typedef typename ElementType::type type;
};


template
struct ElementType<0, T>
{
  typedef typename T::HeadType type;
};


template < int k,typename Head, typename ... Tail>
typename ElementType >::type& get(MyTuple& t)
{
    return get_class::get(t);
}

template < int k,typename Head, typename ... Tail>
const typename ElementType >::type& get(const MyTuple& t)
{
    return get_class::get(t);
}

 使用方式：

    MyTuple t(2.1,0,1.11,6666,"helloworld z","world");
    cout << get<0>(t) << get<1>(t) << get<2>(t) << get<3>(t) << get<4>(t) << get<5>(t) << std::endl;
    get<0>(t) = 100;
    get<1>(t) = 10;
    get<4>(t) = "gg world";

    const MyTuple tc(0,0,111.1,5555,"helloworld");
    cout << get<0>(tc) << get<1>(tc) << get<2>(tc) << get<3>(tc) << get<4>(tc) << std::endl;

    cout << get<1>( MyTuple(3.1415926,'c')) << std::endl;