text: #define SOL_CHECK_ARGUMENTS 1
  #include <sol.hpp>
  
  #include "assert.hpp"
  #include <iostream>
  
  int main(int, char*[]) {
  	std::cout << "=== functions empty args ===" << std::endl;
  
  	// sol::reference, sol::Stack_reference,
  	// sol::object (and main_* types) can all be
  	// used to capture "nil", or "none" when a function
  	// leaves it off
  	auto my_defaulting_function = [](sol::object maybe_defaulted) -> int {
  		// if it's nil, it's "unused" or "inactive"
  		bool inactive = maybe_defaulted == sol::lua_nil;
  		if (inactive) {
  			return 0;
  		}
  		if (maybe_defaulted.is<int>()) {
  			int value = maybe_defaulted.as<int>();
  			return value;
  		}
  		return 1;
  	};
  
  	sol::state lua;
  	lua.open_libraries(sol::lib::base);
  
  	// copy function in (use std::ref to change this behavior)
  	lua.set_function("defaulting_function", my_defaulting_function);
  
  	sol::string_view code = R"(
  		result = defaulting_function(24)
  		result_nothing = defaulting_function()
  		result_nil = defaulting_function(nil)
  		result_string = defaulting_function('meow')
  		print('defaulting_function(24), returned:', result)
  		print('defaulting_function(), returned:', result_nothing)
  		print('defaulting_function(nil), returned:', result_nil)
  		print('defaulting_function(\'meow\'), returned:', result_string)
  		assert(result == 24)
  		assert(result_nothing == 0)
  		assert(result_nil == 0)
  		assert(result_string == 1)
  	)";
  
  	lua.safe_script(code);
  
  	std::cout << std::endl;
  
  	return 0;
  }