[Dune] Index to Entity map

[Carsten Gräser]

Hi Kristof,

Am 24.04.2017 um 12:39 schrieb Kristof Cools:
> Dear all,
> 
> I am completely new at Dune and after going through the available docs
> and tutorials I have the following general question:
> 
> I understand that the concept of a mapper/indexset is central to
> dune-grid and allows one to get an index (and corresponding attribute
> values) given an entity. It there a reason that the inverse concept is
> not part of the API? in other words, why is the set of entities merely
> iterable, as opposed to indexable?
there are several reasons which are nicely explained in our FAQ:

  https://dune-project.org/community/faq/

For recent versions of dune the EntityPointer does not
exist anymore. Just ignore corresponding statements. The
rest remains valid.

Best,
Carsten