for_each_function_call.cpp

#include <functional>
#include <iostream>

using namespace std;

template <typename... RetTs, typename... ArgTs>
auto _for_each(std::function<RetTs(ArgTs...)>... funcs)
{
	return [ = ] (ArgTs... args) {
		return tuple {
			funcs(args...)...
		};
	};
}

template <typename... FuncTs>
auto for_each(FuncTs... funcs)
{
	return _for_each(std::function{funcs} ...);
}

auto f1(char a) 
{ 
	cout << a; return '1'; 
}

auto f2(char a) 
{ 
	cout << a; return  2 ; 
}

int main()
{
	auto l1 {[](char a) { cout << a; return '1'; }};
	auto l2 {[](char a) { cout << a; return  2 ; }};
	// testing with lambdas
	auto rets {for_each(l1, l2)('a')};

	cout << endl << get<0>(rets) << endl;
	cout << get<1>(rets) << endl;

	std::function func1 {l1};
	std::function func2 {l2};
	// testing with std::function`s
	rets = for_each(func1, func2)('a');

	cout << endl << get<0>(rets) << endl;
	cout << get<1>(rets) << endl;
	// testing with ordinary functions
	rets = for_each(f1, f2)('a');

	cout << endl << get<0>(rets) << endl;
	cout << get<1>(rets) << endl;

	return 0;
}