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[John Nilsson]

On Tue, Feb 9, 2010 at 10:05 PM, Neal Gafter <neal at gafter.com> wrote:

> How would you do this using the macro scheme?
>

Given the macro I previously defined. The following would be expanded as
below. But you were right, it was quite instructive. What does it mean to
return concurrently? I guess the right thing to do is to change the macro to
block the first thread waiting for the futures and return from there.

public Collection<Principal> getAttendees() {
    List<Principal> result = new ArrayList<Principal>();
    forEachConcurrently(EventResponse r : getResponses(), threadPool) {
        if (r.mayAttend()) {
            Principal attendee = r.getAttendee();
            synchronized (result) {
                result.add(attendee);
            }
        }
    }
    return result;
}

public Collection<Principal> getAttendees() {
    List<Principal> result = new ArrayList<Principal>();

    final Collection<Callable<Object>> tasks = new
ArrayList<Callable<Object>>();
    final Collection<Future<Object>> futures = new
ArrayList<Future<Object>();
    for(final EventResponse t : getResponses())
    {
        tasks.add(Executors.callable(new Runnable(){public void run() {
                EventResponse r = t; //Slight bug in the macro, should be 'T
retT' not just 'retT'
                forEachConcurrently_1234: {
                    if (r.mayAttend()) {
                        Principal attendee = r.getAttendee();
                        synchronized (result) {
                            result.add(attendee);
                        }
                    }
                }
        }}));
    }
    try {
        futures.addAll(threadPool.invokeAll(tasks));
    } catch (InterruptedException ex) {}
    return result;
}

BR,
John
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