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#include <iostream> // std::cout
#include <type_traits> // std::is_same
#include <vector>
#include <typeinfo> // typeid
#include <cxxabi.h> // abi
template<typename Container, typename Index> // works, but
auto authAndAccess(Container& c, Index i) // requires
-> decltype(c[i]) // refinement
{
return c[i];
}
template<typename Container, typename Index>
auto authAndAccess14(Container& c, Index i)
{
return c[i];
}
template<typename Container, typename Index>
decltype(auto) authAndAccess14_2(Container& c, Index i)
{
return c[i];
}
template<typename Container, typename Index>
decltype(auto) authAndAccess14_2_const(const Container& c, Index i)
{
return c[i];
}
template<typename Container, typename Index> // final
decltype(auto) // C++14
authAndAccess14_perfect(Container&& c, Index i) // version
{
return std::forward<Container>(c)[i];
}
template<class T1, class T2>
void print_is_same() {
std::cout << std::boolalpha << std::is_same<T1, T2>() << '\n';
}
int main()
{
std::vector<float> vec {1.,2.,3.,5.};
typedef decltype(authAndAccess(vec, 2.)) ReturnType;
typedef decltype(authAndAccess14(vec, 2.)) ReturnType14;
typedef decltype(authAndAccess14_2(vec, 2.)) ReturnType14_2;
typedef decltype(authAndAccess14_perfect(std::vector<float> {1.,2.,3.,5.}, 2.)) ReturnType14_perfect;
typedef decltype(authAndAccess14_2_const(std::vector<float> {1.,2.,3.,5.}, 2.)) ReturnType14_2_const;
print_is_same<float, std::remove_reference<ReturnType>::type>();
print_is_same<float, ReturnType>();
print_is_same<float, std::remove_reference<ReturnType14>::type>();
print_is_same<float, ReturnType14>();
print_is_same<float, std::remove_reference<ReturnType14_2>::type>();
print_is_same<float, ReturnType14_2>();
print_is_same<float, std::remove_reference<ReturnType14_perfect>::type>();
print_is_same<float, ReturnType14_perfect>();
int status;
char *realname = abi::__cxa_demangle(typeid(ReturnType14_2_const).name(), 0, 0, &status);
std::cout << realname << "\n";
print_is_same<float, std::remove_reference<ReturnType14_2_const>::type>();
print_is_same<float, std::remove_const<
std::remove_reference<ReturnType14_2_const>::type
>::type>();
print_is_same<float, std::remove_reference<
std::remove_const<ReturnType14_2_const>::type
>::type>();
print_is_same<float, ReturnType14_2_const>();
}
