[Haskell-cafe] Automated Differentiation of Matrices (again)

In [1](this) email thread Edward Kmett and Dominic Steinitz discuss the state of interoperability of `ad` and `hmatric` (or `repa`) with Edward hinting that the 4.0 line of `ad` might improve on the situation. Could someone elaborate on the state of affairs two years later? Florian [1]: https://mail.haskell.org/pipermail/haskell-cafe/2013-April/107561.html