Index variable Template expansion

Https://www.zhihu.com/question/51253466#include <iostream>

#include <fstream> #include <memory> #include <iterator> #include <type_traits> #include < cstdlib> #include <memory> #include <cxxabi.h> #include <type_traits> #include <typeinfo># Ifndef _msc_ver#   include <cxxabi.h> #endif # include <memory> #include <string> #include < Cstdlib>template <class t>std::string type_name () {    typedef typename STD::REMOVE_REFERENCE&LT;T >::type tr;    Std::unique_ptr<char, Void (*) (void*) > own    (#ifndef _msc_ver        Abi::__cxa_demangle (typeID (TR). Name (), nullptr,                &NBS P           nullptr, nullptr), #else         nullptr, #endif       & nbsp std::free   );    std::string r = own! = nullptr? Own.get (): typeID (TR). Name ();    if (std::is_const<tr>::value)       &nbsp R + = "Const";    if (std::is_volatile<tr>::value)         r + = "volatile";  &nbs P if (std::is_lvalue_reference<t>::value)         r + = "&";    else if (std::is_rval Ue_reference<t>::value)         r + = "&&";    return R; Using namespace std;std::string demangle (const char* name); inline std::string demangle (const char* name) {    in T status = -4;    Std::unique_ptr<char, Void (*) (void*) > res    {        ABI: : __cxa_demangle (name, NULL, NULL, &status),        std::free   };    return ( status==0)? Res.get (): name;}

 

Template<int ... >struct indexseq {};template<int N, int ... Indexes>struct makeindexes:makeindexes<n-1, N-1, indexes...>{    makeindexes ()     {&nbs P       Init (Demangle (typeID (this). Name ());   }    void Init (std::string ID)   & nbsp {        std::cout<< "Creating" <<id<<std::endl;   }}; Template<int ... Indexes>struct makeindexes<0, indexes...>{    typedef indexseq<indexes...> type;    Makeindexes ()     {        Init (Demangle (typeID (this). Name ()));   }     void Init (std::string id)     {        std::cout<< "Creating" <<id& lt;<std::endl;   }};int Main () {       makeindexes<3> a;    Makeindexes<3>::type b;    std::cout<< "*************************************" <<std::endl;    Std::cout<<type_name<decltype (a) > () <<std::endl;    Std::cout <<type_name<decltype (b) > () <<std::endl;}

[Email protected]_99_227_centos dev]#./a.outCreating makeindexes<0, 0, 1, 2>*creating makeindexes<1, 1, 2>*creating makeindexes<2, 2>*Creating Makeindexes<3>**************************************makeindexes<3>indexseq<0, 1, 2>

Inheritance Relationship:

Makeindexes<3>: Makeindexes<2, 2>makeindexes<2, 2>: makeindexes<1,1,2>makeindexes<1,1,2 : Makeindexes<0, 0,1,2>

Index variable Template expansion