[Haskell-cafe] vector-space and standard API for vectors
wren ng thornton
wren at freegeek.org
Fri Oct 22 21:11:41 EDT 2010
On 10/22/10 8:46 AM, Alexey Khudyakov wrote:
> Hello everyone!
> It's well known that Num & Co type classes are not adequate for vectors
> (I don't mean arrays). I have an idea how to address this problem.
> Conal Elliott wrote very nice set of type classes for vectors.
> (Definition below). I used them for some time and quite pleased. Code is
> concise and readable.
> > class AdditiveGroup v where
> > zeroV :: v
> > (^+^) :: v -> v -> v
> > negateV :: v -> v
> I'd like to know opinion of haskellers on this and specifically opinion
> of Conal Eliott as author and maintainer (I CC'ed him)
Just my standard complaint: lack of support for semirings, modules, and
other simple/general structures. How come everyone's in such a hurry to
run off towards Euclidean spaces et al.?
I'd rather see,
class Additive v where -- or AdditiveMonoid, if preferred
zeroV :: v
(^+^) :: v -> v -> v
class Additive v => AdditiveGroup v where
negateV :: v -> v
type family Scalar :: * -> *
class Additive v => LeftModule v where
(*^) :: Scalar v -> v -> v
class Additive v => RightModule v where
(^*) :: v -> Scalar v -> v
Though I don't know how much that'd affect the niceness properties you
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