Storing tensors

Even though a user mostly deals with the Tensor{order, dim, T} parameters, the full parameter list for a tensor is actually Tensor{order, dim, T, N} where N is the number of independent elements in the tensor. The reason for this is that the internal storage for tensors is a NTuple{N, T}. In order to get good performance when storing tensors in other types it is important that the container type is also parametrized on N. For example, when storing one symmetric second order tensor and one unsymmetric tensor, this is the preferred way:

struct Container{dim, T, N, M}
    sym_tens::SymmetricTensor{2, dim, T, N}
    tens::Tensor{2, dim, T, M}
end

Leaving out the M and N would lead to bad performance.

immutable VecContainer{dim, T}
    vec::Vec{dim, T}
end