[Dune-devel] [Dune core modules] Doodle: Unify capabilities and type_traits

[Markus Blatt]

On Wed, Dec 03, 2014 at 12:27:17AM +0100, Christian Engwer wrote:
> On Tue, Dec 02, 2014 at 05:44:17PM +0100, Carsten Gräser wrote:
> > Am 02.12.2014 um 14:55 schrieb dune.project at uni-muenster.de:
> Currently I don't see benefits from the change except beauty. Are
> there technical arguments for the change? It is again a place where we
> break user code ... 

I have to second that. Actually, we are doing this kind of changes
quite a lot and often for very small benefit. Still this puts quite a
burden on our users and might upset people (me too, actually) if
there is no clear gain to them. IMHO the same holds for some grid interface
changes for downstream grid developers.

While we are very fast with this kind of changes, we (especially I,
sorry to Tobias and Marco) take a lot of time for well founded
interface changes proposed by users. As everybody has this hard
24-hours-a-day constraint, maybe we should try to focus our precious
time on more pressing/important issues even of they will need a lot
more time from us to sort them out.

Coming back to this particular issue, here are my 2 cents:

- What is the gain from deriving from integral_constant? Or rephrased:
  Want can I do with integral_constant that I cannot do right
  now. Some of the struct do offer additional capabilities,
  e.g. hasSingleGeometryType::topologyId.

- I seems rather consistent in dune-grid as it is or do not all the
  capabilities use ::v? Therefore there might one surprise to first
  time users but once they get it they know how to use it. (Of course
  we can get rid of it, by in addition deriving from integral_constant)

- Changing imposes a lot of changes in user and dune-code.

Markus
-- 
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Dr. Markus Blatt - HPC-Simulation-Software & Services http://www.dr-blatt.de
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