[Haskell-cafe] Re: Functions of type foo :: f a -> g a

[Edward Kmett]

There is also a (naive) metamorphism combinator in my category-extras
library:

http://hackage.haskell.org/packages/archive/category-extras/0.53.4/doc/html/Control-Morphism-Meta-Gibbons.html

Though it is definitely worth pursuing the optimizations that Gibbons talks
about in his very good spigot paper.

Another option might be to rephrase your problem into something suitable to
the Generator/Reducer framework in

http://hackage.haskell.org/package/monoids-0.1.36

Since in many ways if f is a Generator and g is a Reducer, that is exactly
what my monoids api is all about. Though there I admit, I'd need to know
more about the problem domain.

-Edward Kmett

On Thu, May 13, 2010 at 3:32 PM, Stephen Tetley <stephen.tetley at gmail.com>wrote:

> On 13 May 2010 20:25, Gordon J. Uszkay <uszkaygj at mcmaster.ca> wrote:
> [SNIP]
>
> >  The f container is a potentially infinite stream of data obtained from a
> generator, and I want to be able to control how much data is extracted, so
> an eager 'fmap' won't be sufficient (an eager process will be applied to the
> 'chunks' defined by g).
> >
> > I am going to purse the hylomorphism model, but am interested if anyone
> else has any similar situations, and if using classes to manage the
> interface is the right strategy.
>
> Hi Gordon
>
> >From your description this sounds closer to Jeremy Gibbons
> 'metamorphism' than a hylomorphism:
>
> http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/
>
> http://www.comlab.ox.ac.uk/oucl/work/jeremy.gibbons/publications/metamorphisms-scp.pdf
>
> See also the Spigot / pi paper.
>
> Best wishes
>
> Stephen
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