andyli.cpp

#include <numbers>
#include <format>
#include <iostream>
#include <string_view>
#include <string>

namespace impl {
    struct Helper {
        const std::string_view s;
        Helper(const char* s, std::size_t len): s(s, len) {}
        template <typename... Args>
        std::string operator()(Args&&... args) const {
            return std::vformat(s, std::make_format_args(std::forward<Args>(args)...));
        }
    };
} // namespace impl
impl::Helper operator""_f(const char* s, std::size_t len) noexcept {
    return {s, len};
}

int main() {
    std::cout << "乐 :{} *\n"_f(5);
    std::cout << "乐 :{0} {0} *\n"_f(5);
    std::cout << "乐 :{:b} *\n"_f(0b01010101);
    std::cout << "{:*<10}"_f("卢瑟");
    std::cout << '\n';
    int n{};
    std::cin >> n;
    std::cout << "π：{:.{}f}\n"_f(std::numbers::pi_v<double>, n);
}