How to query a constexpr std::tuple at compile time?

Question

In C++0x, one can create a constexpr std::tuple, e.g. like

#include 
constexpr int i = 10;
constexpr float f = 2.4f;
constexpr double d = -10.4;         


        

Answer 1

Now, std::get<> is a constexpr function. The following code compiles for me if I use gcc c++ 11 or above.

constexpr int i2 = std::get<0>(tup);
constexpr std::tuple tup(10, 2.4f, -10.4);

Furthermore, you can generate a list of numbers at compile time by using make_index_sequence (c++14 or above) and access the tuple.

constexpr auto size = std::tuple_size::value;
for_sequence(std::make_index_sequence{}, [&](auto i){
        constexpr auto property = std::get(tup);
        std::cout<
constexpr void for_sequence(std::integer_sequence, F&& f) {
    using unpack_t = int[];
    (void)unpack_t{(static_cast(f(std::integral_constant{})), 0)..., 0};
}