[Dune] [Dune-devel] Reference and pointer type when dereferencing EntityPointer

[Steffen Müthing]

Hi Robert,

Am 20.10.2014 um 10:24 schrieb Robert Kloefkorn <robertk at posteo.de>:

> Hello Steffen,
> 
>> OK, in that case I propose making those return types const. If nobody
>> cries foul until tomorrow, I’ll push the change.
> 
> although your contributions to dune-grid are very welcome you should not
> do interfaces changes in the way you did last week.
> 

yes, maybe I should have put up a vote. On the other hand, I asked about this on
the devel list and the only one who answered was Christian. And his answer was
basically „Oh, that was probably just a cock-up in the original design, we didn’t
know better / correctly think about this back then“.

> Even though the change was obvious it still seems to be open heart
> surgery, especially a non-const to const change calls for trouble.
> Like for any other interface change there must be a vote (doodle) and at
> least a proper notice time (and not something like I'll do it tomorrow).

As I said, the mere fact that the reference was returned this way was a complete surprise
to me - any DUNE code I’ve ever seen binds the return value of a dereferenced iterator or
EntityPointer to a const reference, so I naturally assumed that the returned type was const as
well. And I think at least some others developers thought the same (cf. the discussion on FS#1511).

> 
> So for future changes to the core modules please be more responsible.

Yes, I’ll put up votes in the future. That said, is there a good reason to keep the non-const
reference? I don’t even think we really have a choice here because entities are now copyable.
Think about the following code:

Entity& e1 = *it1;
Entity& e2 = *it2;
e1 = e2;

What does that do to the internal state of it1?

Steffen


> 
> Thanks,
> 
> Robert
> 
> 
> 
> 
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