Re: [boost] Proposed new RAII Library

Subject: Re: [boost] Proposed new RAII Library
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2012-09-15 02:16:07

On Fri, Sep 14, 2012 at 4:19 PM, Vicente J. Botet Escriba
<vicente.botet_at_[hidden]> wrote:
> Le 15/09/12 00:28, Lorenzo Caminiti a écrit :
>
>> On Fri, Sep 14, 2012 at 1:08 PM, Vicente J. Botet Escriba
>> <vicente.botet_at_[hidden]> wrote:
>>>
>>> So resuming, the boost::scope_guard (without a dismiss state) is a
>>> convenient abstraction for c++11 compilers supporting lambdas, and
>>> Boost.ScopeExit reflects the same abstraction for C++03.
>>>
>>> I will be for an extension of Boost.ScopeExit that provides a non-macro
>>> interface, like the one of the preceding scope_guard, for the people that
>>> don't need to make their code portable to non c++11 compilers. I will
>>> name
>>> it however scoped_exit.
>>>
>>> Extracted from the Boost.ScopeExit
>>>
>>>
>>> struct  scope_exit  {
>>>      scope_exit(std::function<void  (void)>  f)  :  f_(f)  {}
>>>      ~scope_exit(void)  {  f_();  }
>>> private:
>>>      std::function<void  (void)>  f_;
>>> };
>>
>> void world::add_person(person const& a_person) {
>>       bool commit = false;
>>
>>      persons_.push_back(a_person);
>>      scope_exit on_exit1([&commit, this](void) { // Use C++11 lambda.
>>          if(!commit) persons_.pop_back(); // `persons_` via captured
>> `this`.
>>      });
>>
>>      // ...
>>
>>      commit = true;
>> }
>>
>> Sure if there's enough interest I can move this scope_exit class from
>> the examples into the Scope Exit lib itself when #ifndef
>> BOOST_NO_LAMBDAS.
>>
>> My _personal_ opinion is that such a boost::scope_exit class is so
>> trivial that programmers can just program it themselves, but that's
>> just my opinion and I'm happy to add such a feature (or better to move
>> it into the lib from the examples) if Boosters want it. No review
>> should be needed, I can just post the (trivial) changes on this ML and
>> confirm them with Alexander Nasonov.
>
> Lorenzo, thanks for volunteering but the design and implementation is far
> more complex than the extract from the doc. If we want it to be efficient,
> it shouldn't use boost.function, boost/multi_index/detail/scope_guard.hpp
> should be a good staring point.

I see. Then (speaking personally) it might make sense for it to exist
in a lib as its impl is not trivial due to the optimization efforts.
However, I probably won't have time to add this feature to Scope
Exit...

Thanks.
--Lorenzo