Re: [boost] N2346 - Defaulted and Deleted Functions emulation

Subject: Re: [boost] N2346 - Defaulted and Deleted Functions emulation
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-03-02 13:51:40

----- Original Message ----- 
From: "David Abrahams" <dave_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Monday, March 02, 2009 3:18 PM
Subject: Re: [boost] N2346 - Defaulted and Deleted Functions emulation

> 
> 
> on Sun Mar 01 2009, "vicente.botet" <vicente.botet-AT-wanadoo.fr> wrote:
> 
>> My concern is that:
>>
>>     #define BOOST_DEFAULT_CONSTRUCTOR_DEFAULT(T) inline T(){};
>>
>> emulates the syntax but not the semantics of
>>
>>     #define BOOST_DEFAULT_CONSTRUCTOR_DEFAULT(T) T()=default;
>>
>> The point of using the C++0x T()=default syntax is probably to ensure
>> that the class is a POD.
>>
>> In C++03, the class designer has to make a design tradeoff. If
>> providing a default constructor is more important than making the
>> class a POD, then your emulation is OK. But if the priorities are the
>> other way around, then the macro should just eliminate the default
>> constructor.
> 
> Really the only likely use is to ensure POD-ness, because after all "{}"
> is a lot easier to type and read than "=default;"
> 
> One thing we could do in the macro is to
> 
>  BOOST_MPL_ASSERT((boost::is_pod<T>))
> 
> Of course, if you know enough about your implementation you can
> specialize boost::is_pod<YourType> (with the usual caveats if you get it
> wrong).
> 
> I'm not sure it'd be worth it though.

You are right these are little things that the developer could do by himself. I'll however try to introduce yous improvements.

Thanks,
Vicente