dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Sep 29, 2009 at 01:01:35PM +0100, Garth N. Wells wrote:
>
>
> Anders Logg wrote:
> > On Tue, Sep 29, 2009 at 12:42:54PM +0100, Garth N. Wells wrote:
> >>
> >> Anders Logg wrote:
> >>> On Tue, Sep 29, 2009 at 07:39:01AM +0100, Garth N. Wells wrote:
> >>>> Is there a reason why the MeshFunction.get(..) functions return by value
> >>>> rather then reference, e.g. it is currently
> >>>>
> >>>>      inline T get(const MeshEntity& entity) const
> >>>>
> >>>> rather than
> >>>>
> >>>>      inline T& get(const MeshEntity& entity) const
> >>>>
> >>>> Garth
> >>> Yes, we have a set() function for setting the values.
> >>>
> >> I know, but I would like to get a reference rather than copying data
> >>
> >>     unsigned int index = 3;
> >>     const std::vector<double>& vec =  mesh_function.get(index)
> >>
> >> I can do this when I have the MeshEntitiy, but not when using the index.
> >
> > Does it work if you do
> >
> >   &vec[0] = mesh_function.values();
> >
>
> Probably, bit it's not what I want. I have a std::vector attached to
> mesh entities (MeshFunction<std::vector<double> >). I want a reference
> to the std::vector attached to a particular entity
>
>    std::vector<double> vec& =  mesh_function(my_entity);
>
> is fine, but
>
>    std::vector<double> vec& =  mesh_function.get(my_index);
>
> is not.

What if you just add operator[] for uint?

> Back to my question: Is there a reason why MeshFunction::get returns by
> value and not by reference?

There might be a reason. I think we introduced get/set for use in the
Python interface. Perhaps Johan remembers?

--
Anders

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