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#include <type_traits>
 
template <typename...>
struct typelist {};
 
template <typename, int>
struct pair {};
 
template <int... I>
struct indices {
    typedef indices<I..., sizeof...(I)> next;
};
 
template <int N>
struct indices_upto {
    typedef typename indices_upto<N-1>::type::next type;
};
template <>
struct indices_upto<0> {
    typedef indices<> type;
};
 
template <typename T>
struct indices_for;
template <template <typename...> class TT, typename... T>
struct indices_for<TT<T...>> : indices_upto<sizeof...(T)> {};
 
template <typename, typename>
struct zip;
template <template <typename...> class TT, typename... T, template <int...> class TI, int... I>
struct zip<TT<T...>, TI<I...>> {
    static_assert(sizeof...(T) == sizeof...(I), "sizes must match");
    typedef typelist<pair<T,I>...> type;
};
 
 
template <int I, typename List>
struct element_impl;
 
template <typename... TL, int... IL, typename T, int I, typename... TR, int... IR>
struct element_impl<I, typelist<pair<TL,IL>..., pair<T,I>, pair<TR,IR>...>> {
    typedef T type;
};
 
template <int I, typename List>
struct element
: element_impl<I, typename zip<List, typename indices_for<List>::type>::type> {};
 
#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
 
typedef typelist<int, double, char, float, long> list;
typedef typename element<0, list>::type should_be_int;
typedef typename element<1, list>::type should_be_double;
typedef typename element<2, list>::type should_be_char;
typedef typename element<3, list>::type should_be_float;
typedef typename element<4, list>::type should_be_long;
 
STATIC_ASSERT(std::is_same<should_be_int, int>::value);
STATIC_ASSERT(std::is_same<should_be_double, double>::value);
STATIC_ASSERT(std::is_same<should_be_char, char>::value);
STATIC_ASSERT(std::is_same<should_be_float, float>::value);
STATIC_ASSERT(std::is_same<should_be_long, long>::value);
 
int main() {}

prog.cpp: In instantiation of 'element<0, typelist<int, double, char, float, long int> >':
prog.cpp:52:34:   instantiated from here
prog.cpp:47:79: error: invalid use of incomplete type 'struct element_impl<0, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:38:8: error: declaration of 'struct element_impl<0, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:52:36: error: 'type' in class 'element<0, typelist<int, double, char, float, long int> >' does not name a type
prog.cpp:52:54: error: invalid type in declaration before ';' token
prog.cpp: In instantiation of 'element<1, typelist<int, double, char, float, long int> >':
prog.cpp:53:34:   instantiated from here
prog.cpp:47:79: error: invalid use of incomplete type 'struct element_impl<1, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:38:8: error: declaration of 'struct element_impl<1, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:53:36: error: 'type' in class 'element<1, typelist<int, double, char, float, long int> >' does not name a type
prog.cpp:53:57: error: invalid type in declaration before ';' token
prog.cpp: In instantiation of 'element<2, typelist<int, double, char, float, long int> >':
prog.cpp:54:34:   instantiated from here
prog.cpp:47:79: error: invalid use of incomplete type 'struct element_impl<2, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:38:8: error: declaration of 'struct element_impl<2, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:54:36: error: 'type' in class 'element<2, typelist<int, double, char, float, long int> >' does not name a type
prog.cpp:54:55: error: invalid type in declaration before ';' token
prog.cpp: In instantiation of 'element<3, typelist<int, double, char, float, long int> >':
prog.cpp:55:34:   instantiated from here
prog.cpp:47:79: error: invalid use of incomplete type 'struct element_impl<3, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:38:8: error: declaration of 'struct element_impl<3, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:55:36: error: 'type' in class 'element<3, typelist<int, double, char, float, long int> >' does not name a type
prog.cpp:55:56: error: invalid type in declaration before ';' token
prog.cpp: In instantiation of 'element<4, typelist<int, double, char, float, long int> >':
prog.cpp:56:34:   instantiated from here
prog.cpp:47:79: error: invalid use of incomplete type 'struct element_impl<4, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:38:8: error: declaration of 'struct element_impl<4, typelist<pair<int, 0>, pair<double, 1>, pair<char, 2>, pair<float, 3>, pair<long int, 4> > >'
prog.cpp:56:36: error: 'type' in class 'element<4, typelist<int, double, char, float, long int> >' does not name a type
prog.cpp:56:55: error: invalid type in declaration before ';' token
prog.cpp:59:1: error: static assertion failed: "std::is_same<should_be_double, double>::value"
prog.cpp:60:1: error: static assertion failed: "std::is_same<should_be_char, char>::value"
prog.cpp:61:1: error: static assertion failed: "std::is_same<should_be_float, float>::value"
prog.cpp:62:1: error: static assertion failed: "std::is_same<should_be_long, long>::value"

Standard output is empty