Howard Hinnant wrote:
On Jul 7, 2004, at 1:45 PM, Peter Dimov wrote:
My proposal (I'm not sure whether I should be credited for it; Howard posted locks that had these properties and I merely commented) can be made to break such code at compile time, simply by removing the nested TryMutex::scoped_try_lock typedef (as there is no longer a need for it, because ::scoped_lock is a TryLock or TimedLock, as appropriate).
Interesting... I hadn't thought about doing that. But I think I see where you're headed. A lock is just a lock, those parts of it you need, you instantiate and use. Those parts you don't, you ignore and they don't hurt anything (unless you try to explicitly instantiate your lock). If you try to use something the templated mutex doesn't support, you get a compile time error. Giving that some more thought...
Yes, it's even possible to collapse all locks into one templated class. My point was weaker than that. I wanted to collapse all three locks exposed by a TimedMutex into one, since with the linear concept hierarchy, there is no longer any reason to expose separate locks. A single TimedLock - called TimedMutex::scoped_lock - will suffice. Generic code that only needs a Mutex or TryMutex can still operate on a TimedMutex.