#### post (2 of 3 overloads)

Submits a completion token or function object for execution.

    template<
        typename Executor,
        typename CompletionToken = DEFAULT>
    DEDUCED post(
        const Executor & ex,
        CompletionToken && token = DEFAULT,
        typename constraint< execution::is_executor< Executor >::value||is_executor< Executor >::value >::type  = 0);

This function submits an object for execution using the specified executor. The function object is queued for execution, and is never called from the current thread prior to returning from `post()`.

The use of `post()`, rather than `defer` , indicates the caller's preference that the function object be eagerly queued for execution.

This function has the following effects:

- Constructs a function object handler of type `Handler`, initialized with `handler(forward<CompletionToken>(token))`.
- Constructs an object `result` of type `async_result<Handler>`, initializing the object as `result(handler)`.
- Obtains the handler's associated executor object `ex1` by performing `get_associated_executor(handler)`.
- Creates a work object `w` by performing `make_work(ex1)`.
- Obtains the handler's associated allocator object `alloc` by performing `get_associated_allocator(handler)`.
- Constructs a function object `f` with a function call operator that performs `ex1.dispatch(std::move(handler), alloc)` followed by `w.reset()`.
- Performs `Executor(ex).post(std::move(f), alloc)`.
- Returns `result.get()`.