Building a variant visitor - https://arne-mertz.de/2018/05/overload-build-a-variant-visitor-on-the-fly/

overload.example.hpp

#include "overload.hpp"

#include <iostream>
#include <string>
#include <variant>

int main() {
    using namespace cmuoh;
    std::variant<int, float, std::string> intFloatString { "Hello" };
    std::visit(overload  {
        [](const int& i) { std::cout << "int: " << i; },
        [](const float& f) { std::cout << "float: " << f; },
        [](const std::string& s) { std::cout << "string: " << s; }
      },
      intFloatString
    );        
}

overload.hpp

#ifndef CMUOH_OVERLOAD_HPP_
#define CMUOH_OVERLOAD_HPP_

namespace cmuoh {

template <class ...Fs>
struct overload : Fs... {
  template <class ...Ts>
  overload(Ts&& ...ts) : Fs{std::forward<Ts>(ts)}...  {} 

  using Fs::operator()...;
};

template <class ...Ts>
overload(Ts&&...) -> overload<std::remove_reference_t<Ts>...>;

} //namespace "cmuoh"

#endif //CMUOH_OVERLOAD_HPP_