HierarchicalMatrices should use BlockArrays

[dlfivefifty]

BlockArrays has a well-developed block matrix structure, so this would avoid needing your own Block.

[MikaelSlevinsky]

You're talking mainly about the abstract block array interface, and not the concrete block array type, right? AFAICT, hierarchical matrices are block arrays where the blocks are different types, but this is staged for performance. On the other hand, the concrete block array type has templated the block type. I don't see how a getindex on the blocks would ever be performant for hierarchical matrices due to the type instability. setindex!, though is type stable.

[dlfivefifty]

I meant HierarchicalMatrix{T} <: AbstractBlockMatrix{T}.