dolfin team mailing list archive

[Benjamin Kehlet <benjamik@xxxxxxxxx>]

2012/8/20 Anders Logg <logg@xxxxxxxxx>:
> On Mon, Aug 20, 2012 at 05:00:32PM +0100, Garth N. Wells wrote:
>> On 20 August 2012 16:50, Anders Logg <logg@xxxxxxxxx> 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)
>> >     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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