# dlib C++ Library - async.h

    // Copyright (C) 2016  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_AsYNC_Hh_
    #define DLIB_AsYNC_Hh_

    // C++11 things don't work in old versions of visual studio
    #if !defined( _MSC_VER) ||  _MSC_VER >= 1900

    #include "async_abstract.h"
    #include "thread_pool_extension.h"
    #include <future>
    #include <functional>

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        namespace impl
        {
            template <typename> struct result_of;

    #if (__cplusplus >= 201703L ||                          \
         (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)) && \
        __cpp_lib_is_invocable >= 201703L
            template <typename F, typename... Args>
            struct result_of<F(Args...)> : std::invoke_result<F, Args...> {};
    #else
            template <typename F, typename... Args>
            struct result_of<F(Args...)>
                    : std::result_of<F&&(Args&&...)> {};
    #endif
        }

    // ----------------------------------------------------------------------------------------

        thread_pool& default_thread_pool();

    // ----------------------------------------------------------------------------------------

        template <
            typename Function,
            typename ...Args
            >
        std::future<typename impl::result_of<Function(Args...)>::type> async(
            thread_pool& tp,
            Function&& f,
            Args&&... args
        )
        {
            using return_type   = typename impl::result_of<Function(Args...)>::type;
            using task_type     = std::packaged_task<return_type()>;
            auto task = std::make_shared<task_type>(std::bind(std::forward<Function>(f), std::forward<Args>(args)...));
            auto ret  = task->get_future();
            tp.add_task_by_value([task]() {(*task)();});
            return ret;
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename Function,
            typename ...Args
            >
        std::future<typename impl::result_of<Function(Args...)>::type> async(
            Function&& f,
            Args&&... args
        )
        {
            return async(default_thread_pool(), std::forward<Function>(f), std::forward<Args>(args)...);
        }

    }

    // ----------------------------------------------------------------------------------------

    #ifdef NO_MAKEFILE
    #include "async.cpp"
    #endif

    #endif
    #endif // DLIB_AsYNC_Hh_