Re: [boost] future<>::then() Error returning future<void> (on trunk)

Subject: Re: [boost] future<>::then() Error returning future<void> (on trunk)
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-04-07 18:06:38

Le 07/04/13 23:41, Fernando Pelliccioni a écrit :
> On Mon, Apr 1, 2013 at 2:09 PM, Vicente J. Botet Escriba <
> vicente.botet_at_[hidden]> wrote:
>
>> Le 22/01/13 22:56, Vicente Botet a écrit :
>>
>>   Fernando Pelliccioni wrote
>>>> Hi Vicente, hi all,
>>>>
>>>> I noticed that in the trunk  there is a implementation of
>>>> future<>::then().
>>>> Thank you very much for your efforts to implement it!
>>>>
>>> Hi Fernando,
>>>
>>> I have started with a restricted implementation. While trying to cover
>>> with
>>> the whole requirements I didn't reach to get correct implementation. This
>>> is
>>> way this new feature is not delivered yet. For the time been I don't think
>>> the current implementation is ready for production code.
>>>
>>>
>>>   The following example, compiles OK
>>>>       boost::future
>>>> <int>
>>>>    f1 = boost::async([]() { return 123; });
>>>>       f1.then([](boost::future
>>>> <int>
>>>>    const& f) {
>>>>               return std::string("");
>>>>       });
>>>>
>>>>
>>>> But this one fails to compile:
>>>>       boost::future
>>>> <int>
>>>>    f1 = boost::async([]() { return 123; });
>>>>       f1.then([](boost::future
>>>> <int>
>>>>    const& f) {
>>>>       });
>>>>
>>>> Here future<>::then() have to returns future
>>>> <void>
>>>>    like ...
>>>>
>>>>         boost::async([]() {  });
>>>>
>>>> Am I right?
>>>>
>>> Yes, it should. I have no access to my development environment for this
>>> week. Could you post the compiler error?
>>>
>>>
>>>   On the other hand, have you taken into account the following paper?
>>>>       http://www.open-std.org/jtc1/**sc22/wg21/docs/papers/2012/**
>>>> n3451.pdf<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3451.pdf>
>>>>
>>> I read it and the mail exchanges related to this paper.
>>> Currently I didn't reached to make it working at all when the future
>>> destructor blocks, but I'm not  sure this is the hidden problem as I have
>>> also other issues when the future destructor doesn't blocks.
>>>
>>> I'm really sorry that the current state is not really usable :(
>>>
>>>   Hi Fernando,
>> I have reworked the future::then function, and even if it is not yet
>> complete (e.g. deferred is not implemented for c++98 compilers) it start to
>> be usable for c++11 compilers, even if BOOST_THREAD_DONT_PROVIDE_**FUTURE_INVALID_AFTER_GET
>> is not defined. BTW, joining on the async future destructor works also.
>>
>> Please could you give it a try and let me know whatever you can find that
>> doesn't works as you expect,
>>
>> Best,
>> Vicente
>>
>>
>>
> Hi Vicente,
>
> Sorry for the delay!
>
> It works fine !!
>
> Thanks!
>

Glad to hear it is working for you.
I would try to merge it to release tomorrow after running the regression 
test (if there is yet time to merge).

Best,
Vicente