Should BlockArray(arr::AbstractArray{T,N},..) always create a BlockArray{T,N,Array{T}}?

[dlfivefifty]

At the moment BlockArray(arr::AbstractArray{T,N},..) creates a BlockArray{T,N,typeof(arr)}. However, for many types subarrays are not of the same type (e.g., Diagonal). I think it is safer to always convert to Array.

The one argument I can see is that it might be nice for BlockArray(::SparseVector) to automatically use sparse data storage.

Another option is to look into whether the type of sub-blocks can be inferred automatically.

[KristofferC]

Hm, we should probably to some type promotion then. Is typejoin the correct function?

[dlfivefifty]

No I don't think so. In the case of N = 1 this could be done by comprehension:

[arr[globalrange(block_sizes, K)] for K=1:nblocks(block_sizes,1)]

should automatically infer the correct type (SparseVector if arr is a SparseVector, otherwise normally Vector).

I'm not sure how to do comprehension via generated functions though.