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From: Peter Dimov (pdimov_at_[hidden])
Date: 2003-02-08 13:29:29

David Abrahams wrote:
> "Peter Dimov" <pdimov_at_[hidden]> writes:
>> Using an undefined-yet Executor concept for the first argument. This
>> is not much different from
>> async_call<int> f( bind(g, 1, 2) );
>> // execute f using whatever Executor is appropriate
>> int r = f.result();
>> except that the async_call doesn't need to know about Executors.
> ...and that you don't need a special syntax to get the result out that
> isn't compatible with functional programming. If you want to pass a
> function object off from the above, you need something like:
> bind(&async_call<int>::result, async_call<int>(bind(g, 1, 2)))

Hmm. Actually I'll need a similar three-liner:

async_call<int> f( bind(g, 1, 2) );
// execute f using whatever Executor is appropriate
// pass bind(&async_call<int>::result, &f) to whoever is interested

Synchronous RPC calls notwithstanding, the point of the async_call is that
the creation+execution (lines 1-2) are performed well in advance so that the
background thread has time to run. It doesn't make sense to construct and
execute an async_call if the very next thing is calling result(). So in a
typical scenario there will be other code between lines 2 and 3.

The bind() can be syntax-sugared, of course. :-)

>>> int r = async_call<int>(create_thread(), bind(g, 1, 2));
>>> int r = async(boost::thread(), g, 1, 2);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> int r = async_call<int>(rpc(some_machine), bind(g,1,2));
>>> int r = async_call<int>(my_message_queue, bind(g,1,2));
>> All of these are possible with helper functions (and the <int> could
>> be made optional.)
> Yup, note the line in the middle.

The line in the middle won't work, actually, but that's another story.
boost::thread() creates a "handle" to the current thread. ;-) Score another
one for defining concepts before using them.

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