A single function that uses a bunch of C++11/14 features and for "old-school" C++ developers will not even read like C++ anymore.Specifically, it uses:- lambda functions (C++11) with generalized capture semantics (C++14)- rvalue references (C++11)- auto variables (C++11)- decltype and trailing function return type syntax (C++11)- std::move and s…

cpp11.cpp

#include <iostream>
#include <future>

using namespace std;

template <typename Fn, typename... Args>
auto do_async_with_log(ostream& os, Fn&& fn, Args&&... args) ->
	future<decltype(fn(args...))>
{
	os << "[TID=" << this_thread::get_id()
	   << "] Starting to invoke function..." << endl;
	auto bound = bind(fn, forward<Args&&...>(args...));
	return async([b=move(bound),&os]() mutable {
		auto result = b();
		os << "[TID=" << this_thread::get_id()
		   << "] ...invocation done, returning " << result << endl;
		return result;
	});
}

@pmalek pass it an ostream, a functor and arguments and it will execute:

auto check_answer = [](int x) { return x == 42; };
auto future_answer = do_async_with_log(cout, check_answer, 41);
return future_answer.get();

But I do have a few comments.

• On line 12 the correct syntax is forward<Args>(args)...

• async has this kind of bind functionality built-in so I would consider using it:

  return async([fn = forward<Fn>(fn), &os](auto&&... args) {
      auto result = fn(forward<decltype(args)>(args)...);
      os << ...
      return result;
  }, forward<Args>(args)...);

But on second thought it seems that bind minimizes the amount of forward spam, so good job on thinking of that one.