[dune-functions] Interface limitations in the functions interface

[Carsten Gräser]

Hi Christian,

Am 19.03.2015 um 21:54 schrieb Christian Engwer:
>> I also wanted to do this for GridFunction and LocalFunction, but
>> did not find a working solution. But I can't remember the reason
>> now. Making the base class a template parameter of the wrapper
>> should work.
> 
> That was kind of my idea. I thought that the type-erasure class could
> get a pair of classes, which should be injected as base classes for
> the interface and for the wrapper. These classes would have to be
> template template parameters, as we would still have to specify the
> main interface class, in order to inject the lower-level interfaces,
> or the other way around...
I just tried this again and now it seems to work - at least
for implementing LocalFunction by injecting the interface and
implementation. I'll clean this up and implement LocalFunction
and GridFunction using this approach tomorrow. For now I'll
do this in the current master branch. But it should work
exactly the same for your new branch.

Best,
Carsten