Note effect of BOOST_USE_SEGMENTED_STACKS if StackAllocator is not explicitly
passed.
Introduce function_heading_for QuickBook template to allow separate
descriptions of swap(fiber), swap(packaged_task) and swap(promise).
Document async() using C++14 std::result_of_t and std::decay_t, aligning with
std::async() documentation.
Rework when_any / when_all examples to use unbounded_channel throughout, since
we always close() the channel after the first value anyway. bounded_channel
doesn't really add much value here.
Make wait_first_outcome_impl() infer its channel pointer type. That way we can
reuse that function instead of coding a separate wait_all_until_error_impl(),
which differs only in using the nchannel facade instead of directly pushing to
unbounded_channel.
Explain use of std::bind() to bind a lambda.
Use a more nuanced discussion of promise lifetime in write_ec() example
function.
Use condition_variable::wait(lock, predicate) in a couple places in
work_sharing.cpp example.
Passing the futures from the argument-pack functions through a function-call
boundary forces the runtime to perform all the async() calls _first,_ then
make a separate pass through the futures to obtain results.
Introduce Runner and Example classes to collect and ultimately run lambdas
illustrating use of each different wait_something() variant.
Move Verbose up to the top for use by Runner. Similarly, move sleeper() for
use by those lambdas.
The body of main() then reduces to a Runner::run() call.
Now that wait_first_simple() is again based on Done (a bool protected by a
condition variable) rather than a barrier(2), have to introduce
wait_all_simple_impl() to manage the barrier.
This reverts commit 59a3afd209, reinstating the
Done wrapper.
While it is true that a barrier(2) will wake up when the second fiber calls
wait(), it then _resets._ This means that the _third_ fiber will wait() for
the fourth, and so on. If an odd number of fibers binds that barrier, the last
of them will hang until shutdown.
We want Done.wait() to wake up on the first notify() call, and for every
subsequent notify() call to be a no-op. Apparently Done is the correct
mechanism after all.
We now have:
wait_any_value(): for when passed functions cannot throw exceptions;
wait_first_outcome(): get earliest result/exception;
wait_first_success(): get first non-exception result.
