源码展示:
#include <iostream> using namespace std; template <typename ... Args> struct typelist; typedef typelist <int ,short ,double ,long ,float> defaultPolicys; template <typename A, typename B> struct concat; template <typename... A, typename... B> struct concat<typelist<A...>, typelist<B...> > { typedef typelist<A..., B...> type; }; template<typename T, typename... TList> struct concat<typelist<TList...>, T > { typedef typelist<TList..., T> type; }; template<typename T, typename... TList> struct concat< T, typelist<TList...> > { typedef typelist<T, TList...> type; }; template <typename T ,int I, typename K= defaultPolicys> struct replace; template <typename T, int I, typename H,typename ...Tail> struct replace<T,I,typelist<H,Tail...>> { typedef typename concat<H, typename replace<T, I-1, typelist<Tail...>>::type>::type type; }; template <typename T,typename H,typename... Tail> struct replace<T,0,typelist<H,Tail...>> { typedef typelist<T,Tail...> type; }; template <typename T ,int I> struct Custom { const static int index = I; typedef T newType; }; template <typename ...> struct CEO; template <> struct CEO<> { typedef defaultPolicys myPolicys; }; template <typename T> struct CEO<T> { typedef typename replace<typename T::newType,T::index>::type myPolicys; }; //template <typename T,typename U> struct CEO<T,U>{ typedef typename replace<typename U::newType,U::index,typename CEO<T>::myPolicys>::type myPolicy;}; template <typename T,typename ... Tail> struct CEO<T,Tail...> { typedef typename replace<typename T::newType,T::index,typename CEO<Tail...>::myPolicys>::type myPolicys; }; int main() { typedef typelist <int ,short ,double ,long ,float> five; typedef typelist <int ,short ,string, char ,string> fives; if(is_same<typename CEO<>::myPolicys,five>::value)cout<<"..."<<endl; if(is_same< CEO< Custom<string,2>,Custom<char,3>,Custom<string,4> > ::myPolicys,fives>::value)cout<<"..."<<endl; return 0; } |
