相关疑难解决方法(0)

我试图理解以下来自http://en.cppreference.com/w/cpp/utility/variant/visit的例子.

#include <iomanip>
#include <iostream>
#include <string>
#include <type_traits>
#include <variant>
#include <vector>


using var_t = std::variant<int, long, double, std::string>;

template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
// what is this declaration imply???
template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;

int main() {
    std::vector<var_t> vec = {10, 15l, 1.5, "hello"};


    for (auto& v: vec) {
        std::visit(overloaded {
            [](auto arg) { std::cout << arg << '\n'; },
            [](double arg) { std::cout << std::fixed << arg << '\n'; }, …