make_integer_sequence, C++ (vc++)

make_integer_sequence

#include <cstddef>
#include <type_traits>

template< typename T, T... i >
struct integer_sequence {
    using value_type = T;
    static constexpr std::size_t size = sizeof...( i );
};
namespace detail {
    template< typename T, T i, bool _0 = ( i == 0 ), bool _1 = ( i == 1 ) >
    struct make_integer_sequence_impl {
        static_assert( i >= 0, "make_integer_sequence requires a non-negative size" );
        template< typename = typename make_integer_sequence_impl< T, i / 2 >::type, typename = typename make_integer_sequence_impl< T, i % 2 >::type >
        struct helper {
        };
        template< T... j, T... k >
        struct helper< integer_sequence< T, j... >, integer_sequence< T, k... > > {
            using type = integer_sequence< T, j..., ( j + i / 2 )..., ( k + i - 1 )... >;
        };
        using type = typename helper<>::type;
    };
    template< typename T, T i >
    struct make_integer_sequence_impl< T, i, true, false > {
        using type = integer_sequence< T >;
    };
    template< typename T, T i >
    struct make_integer_sequence_impl< T, i, false, true > {
        using type = integer_sequence< T, 0 >;
    };
}
template< typename T, T N >
using make_integer_sequence = typename detail::make_integer_sequence_impl< T, N >::type;
template< std::size_t N >
using make_index_sequence = make_integer_sequence< std::size_t, N >;
    
int main( int argc, char** argv ) {
    make_integer_sequence< std::size_t, 3 >{};
}


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