template< typename CancellationCondition, typename CompletionToken> auto async_wait( CancellationCondition cancellation_condition, CompletionToken && token);
Launches the group and asynchronously waits for completion.
A function object, called on completion of an operation within the
group, that is used to determine whether to cancel the remaining
operations. The function object is passed the arguments of the completed
operation's handler. To trigger cancellation of the remaining operations,
it must return a
value other than
A completion token whose signature is comprised of a
N> indicating the completion order of the operations, followed
by all operations' completion handler arguments.
The library provides the following