[Haskell-cafe] Restricted type classes

[John Lato]

>
> From: Stephen Tetley <stephen.tetley at gmail.com>
>
> On 6 September 2010 20:18, John Lato <jwlato at gmail.com> wrote:
>
> > Can you give an example of a Functor that doesn't have pure?  I think
> it's
> > Pointed Functors which are useful; not Functor by itself.
>
> Strictly speaking is Pair one? The current implementation tacks on monoid.
>

Interesting example.  I tend not to like implementations which rely on
bottoms, so I think I'd agree.

In a similar spirit, I would propose Data.Vector.Unboxed.Vector as a Pointed
Functor (modulo element restrictions) which is not Applicative, since the
necessary element restrictions mean <*> can't be defined.

John
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20100907/b1372eed/attachment.html