I use breeze's collections (namely DenseVector), in which I have integers and doubles and the like, and use them a little like you might use numpy's arrays. I stumbled upon https://github.com/non/spire. My impression is, it is not so strong on collection, but stronger on types that I might want to put inside of collections - e.g. Interval sounds awesome. Is my impression right and would be combining them a good idea?
From https://mcmap.net/q/1160134/-why-is-densevector-a-mutable-collection I learned that Breeze uses netlib-java to be really fast. Would I destroy that speed if I put descendants of AnyRef (in this case from Spire) into the DenseVectors back-end Arrays instead of descendants of AnyVal?