[Haskell-cafe] vector-space and standard API for vectors
daniel.is.fischer at web.de
Thu Nov 4 11:02:34 EDT 2010
On Thursday 04 November 2010 15:33:09, Jacques Carette wrote:
> On 02/11/2010 8:16 PM, Conal Elliott wrote:
> > > Vector (Complex a) is a vector with respect to both 'a' and 'Complex
> > > a'.
> > Even worse, () is a vector w.r.t. *every* scalar type.
> Why is this bad?
It's bad for making a type class with a "Scalar" type family (or FunDeps).
instance VectorSpace () where
type Scalar () = ???
> () is the canonical 0-dimensional vector space.
> 0-dimensional vector spaces are very useful because they allow quite a
> number of linear algebra algorithms to be stated ``inductively'' with no
> funny special cases.
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