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Hi Carsten,<br>
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<pre wrap="">in fact the assumptions are not at all istl specific;</pre>
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yes I know. But my point is that the backend does make assumptions
about<br>
the linear algebra library.<br>
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<blockquote cite="mid:55F7D629.8000702@mi.fu-berlin.de" type="cite">
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a)All nested containers must provide operator[](size_type).
b)All nested containers up to a certain nesting level
must provide resize(size_type).
c)All containers above this level have static size but no resize().
Hence you could easily use nested standard containers like
'vector<vector<array<double,2>>>' and in the example we really
do use 'vector<vector<char>>'. So 'istl' would be misleading.
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<pre wrap="">However, I am not against vector backends in general. I just don't want
them forced onto users of "simple" bases.
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<pre wrap="">I'd also not add a bunch of backends, just the trivial one that bridges
the gap from the multi-index (1,2,3) to [1][2][3].
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<pre wrap="">Alternatively, we could extend istl to do that for us. istl is all
about nested data structures,
so it would be logical to allow something like operator[](TreePath) there.
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<pre wrap="">On the one hand I like this idea, because it would be very convenient.
But I'm afraid, that people will complain (and perhaps that's partly
true):
"We also have some index access scheme, namely nested operator[].
If we add operator[](MultiIndex) for dune-functions, will we add
also add get(MultiIndex), operator()(MultiIndex), ... if that's
convenient for another library? Just write a wrapper for it!"
For the moment I propose to keep the wrapper in dune-functions
and adjust the basis interface such that we don't need it for
flat indices. And if we are convinced that this is a good
interface, we may propose it for istl.
Best,
Carsten
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