sol2/examples/source/overloading_with_fallback.cpp

#define SOL_ALL_SAFETIES_ON 1
#include <sol/sol.hpp>

#include <iostream>

int func_1(int value) {
	return 20 + value;
}

std::string func_2(std::string text) {
	return "received: " + text;
}

sol::variadic_results fallback(
     sol::this_state ts, sol::variadic_args args) {
	sol::variadic_results r;
	if (args.size() == 2) {
		r.push_back({ ts,
		     sol::in_place,
		     args.get<int>(0) + args.get<int>(1) });
	}
	else {
		r.push_back({ ts, sol::in_place, 52 });
	}
	return r;
}

int main(int, char*[]) {
	std::cout << "=== overloading with fallback ==="
	          << std::endl;

	sol::state lua;
	lua.open_libraries();

	lua.set_function(
	     "f", sol::overload(func_1, func_2, fallback));

	lua.script("print(f(1))");      // func_1
	lua.script("print(f('hi'))");   // func_2
	lua.script("print(f(22, 11))"); // fallback
	lua.script("print(f({}))");     // fallback

	return 0;
}