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

[Gordon J. Uszkay]

The problem does follow a generator / reducer model.   I think between metamorphisms, hylomorphisms and monoids, I should be able to structure my solution correctly.  

Thanks!

Gordon J. Uszkay
uszkaygj at mcmaster.ca



On May 13, 2010, at 3:42 PM, Edward Kmett wrote:

> 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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