Re: C++ Threads, what's the status quo?
* Thant Tessman:
Nicola Musatti wrote:
Lourens Veen wrote:
[...]
So I think that this is really something that has no equivalent in
C++. But on the other hand I can't help but feel somewhat
underwhelmed. The two "threads" remain so tightly coupled that they
can't run in parallel. So I don't really see how this would help C++
take advantage of multicore processors.
I agree. Unless I'm missing something continuations seem to have more
to do with coroutines than with threads.
I'll repeat myself: Continuations are not threads. They are a mechanism
on top of which you can build (among other things) concurrency. This
concurrency can be as tightly coupled (coroutines) or loosely coupled
(threads) as you want.
And I'll repeat myself again: The design of C++ precludes continuations.
No, coroutines, by your own statement above a kind of continuation, have
been implemented for C++ time and time again.
It was very fashionable in a period, to the extent that special language
extensions were deviced and implemented to support "simpler" coroutines;
today, instead of a dash of assembler language + longjmp, or a language
extension, we'd just use the operating system's coroutine support,
either specialized (like window messaging in Windows, very common) or
general (like Windows fibers, very seldom used). In addition it might be
worth noting that cooperative coroutines can be viewed as a restriction
on ordinary threading, providing simpler logic (e.g. few or no problems
with concurrent access), and so cooperative coroutines have been
implemented in terms of threading in Java, both specialized (like
continuations for web programming, if I understand that correctly) and
in more generally applicable form. That can of course also be done in
C++, using a thread library like Boost threads.
The built-in exception mechanism in C++ is described in the Wikipedia
article on continuations as (using) a kind of continuation; presumably
this refers to the catch clause. That seems to indicate you're using
the term "continuation" in a much more specialized sense than the
Wikipedia article. However, exactly what sense is unclear.
"Languages shape the way we think, or don't." -- Erik Naggum
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