• Russ Lewis (28/28) Mar 13 2002 I was thinking about foreach() functions and such, and got to thinking
• Pavel Minayev (6/11) Mar 13 2002 It would be very slooooooow to have garbage collected again and again.

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

I was thinking about foreach() functions and such, and got to thinking
about the possibility of returning an array from a collection object
that would be an array of the iterators of the elements in the
collection.  Then you could iterate through the array, doing something
on each one.

Of course, that array would only be valid as long as the collection
didn't change, which, in a multithreaded program, means you need locks.
So I was ending up with a class (in my head) that wrapped the array.
The collection would get locked when you called GetIteratorArray() or
some such, and it would get automatically unlocked when the destructor
for the class ran.

Of course, this is problematic, since other threads might grab for the
lock and block (since the lock is already owned), and the collection
would not be unlocked until the garbage collector ran.  Thus, we would
need some mechanism to force the GC to run so that the lock would get
released.  I can see a couple of hacks:

* put the waiting thread in a while loop - call the GC, check the lock,
sleep a bit, repeat
* force programmer to delete the array when he's done with it...but if
he does that, then he might as well just have a basic array and manaully
lock/unlock the object

Are there any other ideas how you might do this in D?  I'm hoping for a
very efficient solution with minimal requirements on the programmer.

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"Pavel Minayev" <evilone omen.ru> writes:

"Russ Lewis" <spamhole-2001-07-16 deming-os.org> wrote in message
news:3C8F85A1.3E475065 deming-os.org...

 * put the waiting thread in a while loop - call the GC, check the lock,
 sleep a bit, repeat

It would be very slooooooow to have garbage collected again and again.

 * force programmer to delete the array when he's done with it...but if
 he does that, then he might as well just have a basic array and manaully
 lock/unlock the object

I don't really see any alternatives to this one. Since the lifetime of
your object is not guaranteed in any way when left on its own, it must
be deleted explicitly...