[Dune] leaf entities, iterators and index sets

[Carsten Graeser]

Hello Dune,
I have another question about leaf entities:
Are all subentities of leaf elements leaf entities ?

If this is the case there might be copies of nodes,
edges, faces on different levels which are all leaf entities.
This fits well to the definition of the LeafIndexSet:

	"Leafwise index: Consecutive, zero-starting, non-persistent
	numbering of entities of leaf entities of one codimension and
	geometry type. All children which are copies of an entity have
	the same number."

However this conflicts the definition in the doxygen page
which says that the IndexSet is an injective map. Perhaps
the note on copies from the IdSets page also applies here.
If the above is correct, what is the precise definition of
the LeafIterator ? The doxygen page says:

	"Enables iteration over all leaf entities of a codimension zero of a grid."

I think this (and the typedef GridImp::template Codim< 0 >::Entity Entity)
is wrong and it should be something like:

	"All subentities of leaf elements are leaves. The LeafIterator iterates over
	all leaf entities of the given codimension with the exception that copies
	on different levels are visited only once."

I would adapt the doxygen pages of IndexSet and LeafIterator
if someone who is a more involved grid developer agrees.

Perhaps also the documentation on IdSets should be more explicit
(as the short discussion on the test for FS#211 shows).


Carsten

-- 
----------------------------------------------------------------------
  Carsten Gräser

  Freie Universität Berlin
  FB Mathematik und Informatik (WE II)
  Arnimallee 2-6
  14195 Berlin, Germany

  office: +49-30 / 838-75349
  fax:    +49-30 / 838-54977
  email: graeser at math.fu-berlin.de