Batov, Vladimir wrote:

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Well, as you point out, try_lock is like a timed_lock with time = 0, and lock is like a timed_lock with time = infinity, so why not give timed_lock both lock() and try_lock() methods as shorthand notation for lock(m, t=0) and lock(m, t=infinity)?

[Batov, Vladimir] Because, in my view, it violates the fundamental (and I think widely accepted) OO design principle (guideline?) that in simple terms can be expressed as "one class, one responsibility". Names like Bertrand Meyer, Herb Sutter and many others immediately come to mind.

We can either achieve that by having a universal lock (with timed_lock as the basis) and shorthand notations in separate derived classes (lock, timed_lock and try_lock) or by keeping those three completely unrelated (probably at the expense of some code/functionality duplication). I am personally leaning towards latter, as even though technically all three concepts are related, from the user point of view they are distinct.

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The argument for try_lock not having a blocking lock() method, which you seem to stress more often, is much clearer; I'm much more inclined to agree with you there.

[Batov, Vladimir] Thank you. I feel that it is important that every class does what it promises to do. No more, no less.

For what it's worth, heres a use case I just ran across illustrating why timed_lock should have a blocking lock() method and/or a blocking locked constructor: condition c; void f(mutex m) { mutex::scoped_timed_lock l(m, locked); //always want the lock here for(;;) { //do stuff c.timed_wait(l, next_wakeup_time()); //timed_wait requires a timed_lock } } Mike