So the conclusion is that for a class that has a default constructor, there is
absolutely no difference. But I would be more comfortable if the () were
included.
--
Anders
20 aug 2012 kl. 23:38 skrev Benjamin Kehlet <benja...@simula.no>:
> 2012/8/20 Anders Logg <l...@simula.no>:
>> On Mon, Aug 20, 2012 at 05:00:32PM +0100, Garth N. Wells wrote:
>>> On 20 August 2012 16:50, Anders Logg <l...@simula.no> wrote:
>>>> I'm editing the linear algebra interface to add support for generic
>>>> Krylov matrices and I'm seeing things like this:
>>>>
>>>>
>>>> /// Create empty vector (global)
>>>> boost::shared_ptr<GenericVector> create_vector() const
>>>> {
>>>> boost::shared_ptr<GenericVector> x(new MTL4Vector);
>>>> return x;
>>>> }
>>>>
>>>> /// Create empty vector (local)o
>>>> boost::shared_ptr<GenericVector> create_local_vector() const
>>>> {
>>>> boost::shared_ptr<GenericVector> x(new MTL4Vector);
>>>> return x;
>>>> }
>>>>
>>>> I thought () was required:
>>>>
>>>> boost::shared_ptr<GenericVector> x(new MTL4Vector());
>>>>
>>>> Has this always been the case?
>>>>
>>>
>>> There are some instances where we need to distinguish between local
>>> and distributed vectors, notably in the PETSc interface code. To work
>>> through GenericVector, it appears in the MTL, uBLAS, etc code too.
>>
>> I know, I wasn't referring to the global vs local. I meant omitting
>> the () in constructors that take no arguments:
>>
>> new MTL4Vector()
>>
>> vs
>>
>> new MTL4Vector
>
> Cases exist where the behaviour will be different, but they are rare.
>
> Compare
> http://en.cppreference.com/w/cpp/language/default_initialization
> with
> http://en.cppreference.com/w/cpp/language/value_initialization
>
> (Some examples are given in this answer: http://stackoverflow.com/a/620402 )
>
> Benjamin
>
>>
>> --
>> Anders
>>
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