Christopher Kohlhoff b899f98566 Add experimental::prepend completion token adapter. ...

The prepend completion token adapter can be used to pass additional
before the existing completion handler arguments. For example:

  timer.async_wait(
      boost::asio::experimental::prepend(
        [](int i, std::error_code ec)
        {
          // ...
        },
      42)
    );

  std::future<std::tuple<int, std::error_code>> f = timer.async_wait(
      boost::asio::experimental::prepend(
        boost::asio::use_future,
        42
      )
    );

2021-07-01 10:51:52 +10:00

..

boost

Add experimental::prepend completion token adapter.

2021-07-01 10:51:52 +10:00