BLAS layer about dh-core HOT 4 OPEN

Now this one is difficult, especially if efficiency is important (it is). We will probably end up with different backends with every single once having different constrains on elements which is possible to put into matrices. It's:

• Double, Float, and Complex Double/Float for BLAS
• (Storable a)/(Unbox a) if we're we store data in vectors
• Anything else really. It's only bounded by craziness of backend implementor

Unifying all of these going to be difficult

from dh-core.

We've got to try at least! I have a couple ideas to put on the table for this (based on closed type families).

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@Shimuuar I'm wondering where to put any typeclasses that must be shared between dense-linear-algebra and the main package. In DLA itself, as a new module that will get re-exported ?

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We'll probably split type classes into separate package in the end. But it sounds fine at the moment

BTW I have some BLAS bindings lying around. I should find them

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