Re: [boost] [future William proposal] packaged_task do notacceptboost::ref of a nullary functor

Subject: Re: [boost] [future William proposal] packaged_task do notacceptboost::ref of a nullary functor
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2009-01-05 15:28:18

"vicente.botet" <vicente.botet_at_[hidden]> writes:

> ----- Original Message ----- 
> From: "Anthony Williams" <anthony.ajw_at_[hidden]>
> To: <boost_at_[hidden]>
> Sent: Monday, January 05, 2009 12:49 PM
> Subject: Re: [boost] [future William proposal] packaged_task do notacceptboost::ref of a nullary functor
>
>
>> 
>> "vicente.botet" <vicente.botet_at_[hidden]> writes:
>> 
>>> From: "vicente.botet" <vicente.botet_at_[hidden]>
>> 
>>>> packaged_task do not accept boost::ref to nullary functions while
>>>> thread allows it. Shouldn't packaged_task > accept them? How can
>>>> the user workaround this issue? How thread solved this issue?
>>>
>>> I have found a workaround. Instead of 
>>>     boost::packaged_task<unsigned > tsk(boost::ref(f));
>>> I use
>>>     boost::packaged_task<unsigned> tsk(boost::bind(boost::ref(f)));
>>>
>>> Is this the correct way?
>> 
>> That's essentially what Boost.Thread does.
>
> Given the prototypes:
>     template<typename F> explicit thread(F func);
>
>     template <class F> explicit packaged_task(F const& f):
>
> Shouldn't the prototype of packaged_task be
>     template <class F>
>     explicit packaged_task(F f):
>
> Shouldn't boost::thread(boost::ref(f)); fail or 
> boost::packaged_task<unsigned> tsk(boost::ref(f)); succeed?
>
> What is the reason to make them different?

Hmm. I'm not sure what the difference is with a plain
ref(f). Boost.thread uses bind<void>(f,args) when you specify args in
the constructor, but doesn't do anything for a plain function. I don't
know why it wouldn't work with packaged_task, but I haven't tried it.

I'll investigate.

Anthony
-- 
Anthony Williams
Author of C++ Concurrency in Action | http://www.manning.com/williams
Custom Software Development | http://www.justsoftwaresolutions.co.uk
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