Get the first index of type in the std::tuple<>

gistfile1.cpp

#include <tuple>

// ...

template<typename T, typename C, std::size_t I>
struct tuple_index_r;

template<typename H, typename ...R, typename C, std::size_t I>
struct tuple_index_r<std::tuple<H, R...>, C, I>
    : public std::conditional<std::is_same<C, H>::value,
          std::integral_constant<std::size_t, I>,
          tuple_index_r<std::tuple<R...>, C, I+1>>::type
{};

template<typename C, std::size_t I>
struct tuple_index_r<std::tuple<>, C, I>
{};

template<typename T, typename C>
struct tuple_index_of
    : public std::integral_constant<std::size_t, tuple_index_r<T, C, 0>::value> {};




/// Example

printf("%d\n", tuple_index_of<std::tuple<int, bool, float, int>, int>::value);
printf("%d\n", tuple_index_of<std::tuple<int, bool, float, int>, float>::value);
printf("%d\n", tuple_index_of<std::tuple<int, bool, float, int>, char>::value); // compile error