XML <--> Haskell Data Structure using HXT

[Han Joosten]

I would like to write code to enable importing data to and fro from a Haskell data structure. It makes sense to have some XSD or so that specifies how the XML should be structured. The HDS is already in place. I have been looking into hte HXT library and I think it could be used for this job. However, I am not familiar (yet) with Arrows and the like. Also the use of picklers is new to me. It would help me a lot if someone has a neat example of how coversion between XML and some Haskell data structure can be implemented in het HXT-style.

Do such examples exist? Where can I find them?

For those interested: Here is the Haskell Data Structure: https://sourceforge.net/p/ampersand/code/HEAD/tree/trunk/src/lib/Database/Design/Ampersand/Core/ParseTree.hs 

Cheers & Thanks for reading!

Han Joosten

[Adam Bergmark]

Apparently the original message was sent to the google group, didn't know that existed.  haskel...@haskell.org is the advertised address.

On Thu, Sep 11, 2014 at 2:06 PM, Adam Bergmark <ad...@bergmark.nl> wrote:

Hi Han,

Do you want to control the XML format? If not you can use regular-xmlpickler [1] to derive the serializations automatically.

We have some instances spread around in the rest project [2][3], but we're not doing very complicated things in the manually defined instances afaik.

I'm in no way an hxt expert. It was a bit tricky at first but I managed to write some picklers eventually :-)

Cheers,

Adam

[1] http://hackage.haskell.org/package/regular-xmlpickler

[2] https://github.com/silkapp/rest

[3] https://github.com/silkapp/rest/blob/master/rest-stringmap/src/Rest/StringMap/Util.hs

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[Erik Hesselink]

We use HXT's picklers, and have written a blog post about it [1]. I
just saw that the code isn't formatted that great on our new blog,
I'll see if we can fix that. We also wrote a library [2] for
generically deriving instances for picklers, which we also blogged
about [3]. I hope that helps!

Regards,

Erik

[1] http://engineering.silk.co/post/31921413529/haskell-data-types-and-xml
[2] http://hackage.haskell.org/package/regular-xmlpickler
[3] http://engineering.silk.co/post/31922245822/writing-a-generic-xml-pickler

On Thu, Sep 11, 2014 at 1:57 PM, Han Joosten <han.joo...@gmail.com> wrote:

[Han Joosten]

Thanks a lot for the pointers. They are spot on, and just what I was looking for!

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[Michael Orlitzky]

On 09/11/2014 07:57 AM, Han Joosten wrote:
> I would like to write code to enable importing data to and fro from a
> Haskell data structure. It makes sense to have some XSD or so that
> specifies how the XML should be structured. The HDS is already in place.
> I have been looking into hte HXT library and I think it could be used
> for this job. However, I am not familiar (yet) with Arrows and the like.
> Also the use of picklers is new to me. It would help me a lot if someone
> has a neat example of how coversion between XML and some Haskell data
> structure can be implemented in het HXT-style.
> Do such examples exist? Where can I find them?

I use these extensively in,

http://hackage.haskell.org/package/htsn-import

Each module under the TSN.XML namespace is basically a big XML <->
Haskell converter along with some database stuff.