liwei-cpp / metann Goto Github PK

m_tuple[TagPos] = std::shared_ptr<void>(tmp,
                                    [](void* ptr){
                                        rawVal* nptr = static_cast<rawVal*>(ptr);
                                        delete nptr;
                                    });

#include <iostream>
#include <tuple>

template <typename TSeqCont>
struct Tail_;

template <template <typename...> class Container, typename TH, typename...TCases>
struct Tail_<Container<TH, TCases...>>
{
    using type = Container<TCases...>;
};

template <typename TSeqCont>
using Tail = typename Tail_<TSeqCont>::type;
int main(){
    using Cont=std::tuple<char,long,int>;
    std::cout<<"tail:"<<typeid(Tail<Cont>).name()<<std::endl;
    return 0;
}

#include <iostream>
#include <type_traits>

template < bool AddOrRemoveRef >
struct Fun_;

template <>
struct Fun_< true > {
    template < typename T >
    using type = std::add_lvalue_reference< T >;
};

template <>
struct Fun_< false > {
    template < typename T >
    using type = std::remove_reference< T >;
};

// 注意这里的高级用法
template < typename T >
template < bool AddOrRemoveRef >
using Fun = typename Fun_< AddOrRemoveRef >::template type< T >; //error

// 即使是有别名，还是需要显式说明模板
template < typename T >
using Res_ = Fun< false >;

int main()
{
    Res_< int& >::type h = 3;
    std::cout << h << std::endl;
    return 0;
}