[Haskell-cafe] Re: ANNOUNCE: Haskell XML Toolbox Version 9.0.0
apfelmus at quantentunnel.de
Sat Oct 9 05:04:33 EDT 2010
Gregory Crosswhite wrote:
> Could you explain to me why HXT uses arrows? I have never been able to
> figure out what advantage this gives your library over monads. Since
> your arrows in practice implement ArrowApply, they are really just
> monads anyway, so it seems to me that using arrows instead of monads
> only serves to add complexity to the library without adding any
> benefit. Furthermore, by using arrows instead of monads people cannot
> use the many standard monad libraries out there, but have to instead
> write their own generalizations of them to arrows.
> Is there some benefit that your library gets out of using arrows that I
> missed which makes these costs worth it?
I have the same question.
It looks like the arrows in HXT are typed version of CFilter from
Malcolm Wallace, Colin Runciman.
Haskell and XML: Generic Combinators or Type-Based Translation?
but it appears to me that representing them as
type Filter a b = a -> [b]
allows the use of the list monad, which would highlight the similarity
between list comprehensions and working with XML trees.
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