Re: [boost] Review of Local Exits

Subject: Re: [boost] Review of Local Exits
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2011-11-19 18:39:01

Le 19/11/11 23:08, Lorenzo Caminiti a écrit :
> On Sat, Nov 19, 2011 at 3:59 PM, Alexander Nasonov<alnsn_at_[hidden]>  wrote:
>> This is not a full review of the proposed Boost.Local library, I've
>> reviewed only Local Exits and a potential merge with Boost.ScopeExit.
> Hello Alex and thank you very much for your comments.
>
>> I vote NOT to merge Local Exits with Boost.ScopeExit for the following
>> reasons:
> I have no problem with local exits and scope exits remaining separate.
> Local exits will additionally provide no bindings (void), const
> bindings, and binding of this_.
>
>>   - Local Exits feature gives two different interfaces ("variadic" and
>>     "sequencing"). In my opinion, it should only document C++0X
>>     interface and have a section called something like "What if I don't
>>     have a C++0X compliant compiler?" where it will explain an
> Yes, the same comment was made by Vicente and Thomas for the entire
> Boost.Local. I am happy to just document the variadic syntax and have
> an Annex with the sequencing syntax.
>
>>     alternative interface for a transitional period.
>>     Some compilers already support enough C++0X features to let you
>>     develop a "perfect" interface.
>>   - Binding of variables should be modeled after lambda captures. This
>>     means no this_ and no void. I really like void and I'd added it if
>>     Lorenzo came up with the idea at the time when Boost.ScopeExit was
>>     still in development.
> FYI, I can write pp code that transforms void, this_, etc into lambda
> captures. For example:
>
> TO_CAPTURE(void) // expand to []
> TO_CAPTURE(this_,&x) // expand to [this,&x]
> TO_CAPTURE( (this_) (&x) ) // expand to [this,&x]
>
> This way SCOPE_EXIT(void) and SCOPE_EXIT( (this_) (&x) ) or even
> SCOPE_EXIT(this_,&x) could support void and this_ while still working
> on both C++03 and C++11...
>
>>   - For the same reason, const bind&  and bind&  should be removed from
>>     the interface.
> Well, if local exits are not merged with scope exits, local exits can
> keep const bind&, bind&, this_, void, etc.

Hi Lorenzo,
I wouldn't want two libraries providing Scope Exit idiom in Boost with 
only a minor binding difference, this will be confusing. I don't know if 
you have explained this in the document , but could you try to explain 
here (or point where in the documentation) what are the clear advantages 
of capturing void, this or capturing by const&.

Alex, could you explain why (a part form following the lambda capture), 
you don't want to accept these new bindings in ScopedExit?

Best,
Vicente