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

Subject: Re: [boost] Boost.Fiber review January 6-15
From: Nat Goodspeed (nat_at_[hidden])
Date: 2014-01-22 11:07:43

On Wed, Jan 22, 2014 at 7:30 AM, Vicente J. Botet Escriba
<vicente.botet_at_[hidden]> wrote:

> Le 22/01/14 03:39, Nat Goodspeed a écrit :

>> 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.)

> boost::bind is not movable :( or is it in C++11?)

I haven't yet read Agustín's links -- but I will, thank you!

Since movable-only callables are clearly an important use case, I
would hope that if (let's say) std::bind is not yet itself movable,
that's a transient situation which will soon be remedied.

>> 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?

Again, the material to which Agustín points me may answer this
question. But if using bind() is not an option even internally -- must
Oliver (along with the author of every library that supports user
callables!) reimplement bind() by hand, with support for movable
types?

>> 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?

> From my side this variadic versions must be provided for C++11 compilers at
> least. Any attempt to make the C++98 interface close to the C++11 would be
> welcome.

Agustín, too, says "C++03 support would be nice."

Having myself implemented the preprocessor iteration for a C++03 API
accepting callable-with-up-to-N-args, I know it's a bit of a pain.
Moreover (a key point) anyone invoking the Fiber API who is
constrained to C++03 features will not have movable-only types. In
that scenario, fiber(bind(callable, arg1, arg2)) *is* completely
equivalent to fiber(callable, arg1, arg2).

So when discussing the requested variadic fiber constructor, I will
tease apart the C++11 and C++03 cases. I feel pretty comfortable
stating that the former is much more important than the latter.