find out the type of auto

Question

I am playing with generic lambda in C++1y and I often confused by don\'t know what is the type of auto variable/parameter. Is any good way to find it out?

Answer 1

Use GCC’s __cxa_demangle function:

std::string demangled(std::string const& sym) {
    std::unique_ptr
        name{abi::__cxa_demangle(sym.c_str(), nullptr, nullptr, nullptr), std::free};
    return {name.get()};
}

auto f = [](auto && a, auto b) {
    std::cout << demangled(typeid(decltype(a)).name()) << '\n';
    std::cout << demangled(typeid(decltype(b)).name()) << '\n';
};