Hello, I have been directed to this discussion: http://lists.boost.org/boost-users/2009/08/50601.php when I asked this question before. There are interesting solutions from OvermindDL1 and from Jesse Perla. Basically, define a variant over all the possible multi_array types as: template class multi_array_runtime_dims { typedef variant< multi_array, multi_array, ... multi_array

type;

}; Setting up the extents can be done at runtime as well. I wonder if there has been further thought about the issue, and also what the library designers thinks about it. Regards,