template<typename... Ts>
struct Overloader : Ts...
{
    using Ts::operator()...; // exposes operator() from every base
};

int main()
{
    auto o = Overloader{ [] (auto const& a) {std::cout << a;},
                         [] (float f) {std::cout << std::setprecision(3) << f;} };
}

https://en.cppreference.com/w/cpp/language/using_declaration

不试一下我都看不出这能不能编译通过……
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