conal/vector-space — pull request #5 by andersk (2013-06-04 05:18:59+00:00)
Title: Add HasBasis instances for Maybe, (:->:), (:-*)

`Maybe`, `(:->:)`, `(:-*)` already have `VectorSpace` instances, so why not give them compatible `HasBasis` instances too.

By the way, can I ask why `:-*` is defined in terms of `Sum`? As far as I can tell, the point of `Sum` is to create a `Monoid` instance, but that’s not used or exposed in the context of linear maps. So it seems to just add extra wrapping overhead.