Johannes Waldmann wrote:

I am looking at the Haskell XML RPC library http://www.haskell.org/haxr/ First of all, this is a very nice thing to have, and installation is really easy, using Cabal and the packaged source archives.

Hi Johannes, I'm the maintainer of HaXR, and I'll try to answer your questions as well as I can. I'm moving this thread over to the Haskell Libraries list.

*) Of course I want to dervie XmlRpcType instances automatically. The examples suggest $(asXmlRpcStruct (reifyDecl Person)) but I cannot get this to compile (with ghc-6.4). It seems reifyDecl is gone, and reify has different type. I worked out this:

helper name = asXmlRpcStruct ( ( reify name ) >>= ( \ (TyConI dec) -> return dec ))

$(helper ''Person)

Does xmlrpc.cabal should contain a build-dependency on template-haskell? (Otherwise I get linker errors.)

Thanks for reporting this. I have fixed it in the development version available in the darcs repo at http://cvs.haskell.org/darcs/xmlrpc/ and made a new release today which fixes the TH support.

*) what is the recommended representation that should be created for data T = A { .. } | B { .. } | ... i. e. discriminated unions? Certainly some solution can be coded, but ...

Hmm, I haven't had a need for that yet, so I haven't thought about it. If you come up with a good solution, we could modify THDeriveXmlRpcType to do it automatically.

*) what about the "Java side of things" - perhaps I want (need) to interface to a Java Client. If it's Haskell-to-Haskell, then both server and client of course can derive their XmlRpcType instances from identical data declaraions and everything is fine. For intergration with a different language, what do you recommend: Start from a Haskell data declaration, and derive a Java representation, directly or indirectly? Or start from some language independent data declaration, as it happens (I assume) for JAXB?

Hmm, I guess it's up to you. If you come up with a good solution, or even a tool for autogenerating Haskell types and XmlRpcType instances from som language-independent description, I'll be happy to include it in HaXR. /Björn