[Hs-Generics] xml deserialization using generics?

[Jeremy Gibbons]

Better still is McBride and Paterson's idiomatic traverse, which  
subsumes monadic gmap and a bit more (since some idioms - phantom  
idioms - aren't monads). The serialise/deserialise example is given  
there too.

See Bruno's and my paper "The Essence of the Iterator Pattern".

   http://web.comlab.ox.ac.uk/jeremy.gibbons/publications/#iterator

Jeremy

On 27 Jun 2007, at 09:39, oleg at pobox.com wrote:

>
> Hugh Perkins wrote:
>> Cant decide whether this list is appropriate for questions related to
>> generics usage, or only to generics design?
>
> I think your question is quite appropriate -- actually, it is a good
> question. It asks essentially for a monadic gmap, which seems quite
> important.  This operation is also the `inverse' of one of our
> comparison tests: listify. The latter collects values from the leaves
> of a data type in a list. That list is a `state' of a value, so to
> speak. The state can be transported over the network, and, on the
> other end, can be infused into a prototype object (assuming it has the
> same structure).
>
> The monadic gmap subsumes two traversals: generic map and
> reduction. So, your question looks even better.
>
> I wonder if we should add monadic gmap to our test suite?
>
> I have just committed the monadic gmap implementation and the test for
> one generic library, the one I'm more familiar with. The test is in
> the file
>
>  http://darcs.haskell.org/generics/comparison/SmashA/Deserialize.hs
>
> We start with the data type of a company
>
> C [D "Research" (E (P "Laemmel" "Amsterdam") (S 8000.0))
>     [PU (E (P "Joost" "Amsterdam") (S 1000.0)),
>      PU (E (P "Marlow" "Cambridge") (S 2000.0))],
>    D "Strategy" (E (P "Blair" "London") (S 100000.0)) []]
>
> (see http://darcs.haskell.org/generics/comparison/CompanyDatatypes.hs)
>
> We can serialize it:
>
>  test1 = serialize genCom
>
> obtaining a list
>
>  ["Research","Laemmel","Amsterdam","8000.0","Joost","Amsterdam",
>   "1000.0","Marlow","Cambridge","2000.0","Strategy","Blair",
>  "London","100000.0"]
>
> OTH, we can take the list
>
> retro = ["Metaphysics",
> 	 "Kant","Koeningsberg","800.0",
> 	 "Hume","Edinburgh","100.0",
> 	 "Marlowe","Cambridge","200.0",
> 	 "Ruling","Thatcher","London","50000.0"]
>
> and use it to `upgrade' the company genCom:
>
> test2 = deserialize genCom retro
>
> giving us
>
>  *Deserialize> test2
>  C [D "Metaphysics" (E (P "Kant" "Koeningsberg") (S 800.0))
>     [PU (E (P "Hume" "Edinburgh") (S 100.0)),
>      PU (E (P "Marlowe" "Cambridge") (S 200.0))],
>     D "Ruling" (E (P "Thatcher" "London") (S 50000.0)) []]
>
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