Arrow instance

[ElvishJerricco]

All TASequences can be given instances of Arrow from Control.Arrow.

instance (TASequence s, Arrow a) => Arrow (s a) where
  arr f = tsingleton (arr f)
  first arrs = case tviewl arrs of
    TAEmptyL -> tempty
    a :< as -> first a <| first as

Of course, as with #5, this should be defined per-sequence, instead of with one uber-instance.

[treeowl]

I'm doing a bit of updating in this package and am thinking about this issue. My concern is that Arrow a seems a bit too much. We need to have

blah :: (x -> y) -> a x y
foof :: a x y -> a (x, d) (y, d)
soof :: a x y -> a (d, x) (d, y)

We don't need composition for a, so requiring it to be an Arrow (and therefore a Category) doesn't really feel right. Do you have a specific use-case? Is there a smaller superclass we could use? Or could we write one?