Re: [boost] Boost.Fiber review January 6-15

On 21/01/2014 11:39 p.m., Nat Goodspeed wrote:

On Wed, Jan 15, 2014 at 8:56 PM, Agustín K-ballo Bergé wrote:

...

- The lack of a variadic constructor for `fiber` and variadic arguments for `async` makes it difficult to use the library correctly (even in the presence of C++14 lambdas). The semantic of those calls is that of a deferred call, which is difficult to achieve otherwise (note that `bind` doesn't help here).

The review report (which I am writing now!) does not depend on my understanding this point, but on rereading your mail I realized I do not yet understand it. In my (obviously incomplete) mental model, a hypothetical fiber constructor:

fiber f(some_callable, 3.14, "a string", 17);

would be completely equivalent to:

fiber f(bind(some_callable, 3.14, "a string", 17));

What am I missing? (If this is already well-explained elsewhere, I would appreciate a pointer as much as your own explanation.)

You are missing the support for movable-only type, or the unnecessary copies otherwise. And since you ask for a link, here is one to my own blog: http://talesofcpp.fusionfenix.com/post-14/true-story-moving-past-bind

Oliver may well understand your point already. But if you asked me to implement a variadic fiber constructor (and async() function), I would immediately forward to bind() inside each. Would that be a sufficient implementation? If not, why not?

Here is another link on the subject: http://stackoverflow.com/a/21066704/927034

A broader question to those who requested a variadic fiber constructor (and async()): is it sufficient to provide that support only when the compiler supports variadic templates, or are you asking for the whole ugly C++03 workaround as well?

C++03 support would be nice. Personally, I would be ok with only variadic support, as long as it works on the latest versions of the major compilers (MSVC is the only one where this presents a challenge). Regards, -- Agustín K-ballo Bergé.- http://talesofcpp.fusionfenix.com