Hi!

Breakfast toast: Is there any chance a) and b) below are identical in what they do?


auto mutex = new Mutex();
auto cond = new Condition(mutex);

// a)
synchronized(mutex){
   cond.wait();
}

// b)
mutex.lock();
   cond.wait();
mutex.unlock();


I was sprinkling my code with mutex.lock/unlock (for fun) when suddenly I realized that, hey, maybe synchronized would work just as well, and be even more fun? (If that's even possible.)

BR
/HF

On Wed, 14 Jul 2010 23:22:20 -0400, Heywood Floyd <soul8o8@gmail.com> wrote:

> Hi!
>
> Breakfast toast: Is there any chance a) and b) below are identical in what they do?
>
>
> auto mutex = new Mutex();
> auto cond = new Condition(mutex);
>
> // a)
> synchronized(mutex){
>    cond.wait();
> }
>
> // b)
> mutex.lock();
>    cond.wait();
> mutex.unlock();

Almost, this is more equivalent:

{
  mutex.lock();
  scope(exit) mutex.unlock();
  cond.wait();
}

But yes, the mutex object implements the monitor interface, and replaces its own monitor object with a pointer to itself.

For something really nifty, you can tell mutex to be the monitor object of *any* other object :)  Unfortunately, I can't point you at the docs, cause they dont exist yet, but this will do it:

class C{}

auto c = new C;
auto m = new Mutex(c); // now synchronizing on c is the same as locking m

-Steve

Steven Schveighoffer Wrote:

> On Wed, 14 Jul 2010 23:22:20 -0400, Heywood Floyd <soul8o8@gmail.com> wrote:
> 
> > Hi!
> >
> > Breakfast toast: Is there any chance a) and b) below are identical in what they do?
> >
> >
> > auto mutex = new Mutex();
> > auto cond = new Condition(mutex);
> >
> > // a)
> > synchronized(mutex){
> >    cond.wait();
> > }
> >
> > // b)
> > mutex.lock();
> >    cond.wait();
> > mutex.unlock();
> 
> Almost, this is more equivalent:
> 
> {
>    mutex.lock();
>    scope(exit) mutex.unlock();
>    cond.wait();
> }
> 
> But yes, the mutex object implements the monitor interface, and replaces its own monitor object with a pointer to itself.
> 
> For something really nifty, you can tell mutex to be the monitor object of *any* other object :)  Unfortunately, I can't point you at the docs, cause they dont exist yet, but this will do it:
> 
> class C{}
> 
> auto c = new C;
> auto m = new Mutex(c); // now synchronizing on c is the same as locking m
> 
> -Steve

Cool, love it! Thanks!

/HF