[eigen] Tensor Module: Index mapping support

[Gabriel <gnuetzi@xxxxxxxxx>]

If the user of the tensor component in eigen
uses its own indices lets say

Eigen::Array<int,3> idx(1,2,3);

this is currently not possible:

Eigen::Tensor<double,3> t(4,4,4)
t( idx ) =  5;


We could implement this maybe with the following wrappers
(here for the resize function and CXX11 support of course as example):

                template<typename IndexType>
            void resize( const IndexType & dimensions ){

                resize(dimensions, std::make_index_sequence<NTensorIndices>{} );

            }

            template<typename IndexType, std::size_t... Is>
            void resize(const IndexType & dimensions, std::index_sequence<Is...> )
            {
                m_tensor.resize( dimensions(Is)... );
            }



Or is this already provided in the tensor module such that one can use own index types ?


Thanks a lot :-)

BR Gabriel