fork download

copy

#include <tuple>
 
template <class... T>
struct input
{
    std::tuple<T...> var;
    input(T&&... t) : var(std::forward<T>(t)...) {}
 
    template <
          std::size_t N,
          typename std::enable_if<(N < std::tuple_size<decltype(var)>::value)>::type* = nullptr
     >
    auto get()
          -> typename std::tuple_element<N, decltype(var)>::type&&
    {
        return std::move( std::get<N>(var) );
    }
 
    template <
          std::size_t N,
          typename std::enable_if<(N >= std::tuple_size<decltype(var)>::value)>::type* = nullptr
     >
     void get()
     {
         static_assert(N < std::tuple_size<decltype(var)>::value, "Out of bounds!");
     }
};
 
template <class... Args>
void f(Args&&... args)
{
    auto arguments = input<Args...>(std::forward<Args>(args)...);
 
    arguments.template get<9>(); // returns 2 but I'd rather throw an exception
}
 
int main()
{
    f(2, 4, 6, 8);
}
 

prog.cpp: In instantiation of ‘void input<T>::get() [with unsigned int N = 9u; typename std::enable_if<(N >= std::tuple_size<decltype (((input<T>*)0)->input<T>::var)>::value), void>::type* <anonymous> = 0u; T = {int, int, int, int}]’:
prog.cpp:34:5:   required from ‘void f(Args&& ...) [with Args = {int, int, int, int}]’
prog.cpp:39:17:   required from here
prog.cpp:25:10: error: static assertion failed: Out of bounds!

Standard output is empty