June 2007 - Generics - Haskell.org

xml deserialization using generics?
by Hugh Perkins 03 Jul '07

03 Jul '07

Cant decide whether this list is appropriate for questions related to generics usage, or only to generics design? So let me know if I should use haskell(a)haskell.org instead, but on the other hand I figure you guys are the experts :-) Trying to write an xmlserialization function for arbitrary (Data) objects, and not requiring a DTD or a code generation step. It's possible in C# so it really ought to be possible in Haskell ;-) xml serialization is pretty easy, see section 9.1.1 of http://www.haskell.org/haskellwiki/HXT On the other hand deserialization is still a work in progress. At least I'm not smart enough to figure it out, and nothing comes up in Google. The xml parsing bit is done, see section 9.1.2 of http://www.haskell.org/haskellwiki/HXT So, we can get a list of pairs/triples etc containing the data of our choice, such as field names, field values (in string format), data types, constructors, etc. What's remaining is to take makeConstrM, our final data type, and the list of field values, and to create the final object. Here's my non-working attempt at this bit so far. Most of the working bits come from a demonstration by kpreid in irc yesterday night of using makeConstrM with a pair of strings. The rest of the code is my feeble attempt to get this working for the Config custom data type. runM' :: (MonadState [String] m, Monad m, Data a) => m a runM' = do value <- gets head modify tail -- then one of: (pick the non-working function of your choice ;-) : -- return read (fromJust value) -- return (fromJust $ cast value ) -- return (fst $ head $ gread( "(" ++ value ++ ")" ) ) -- return (fromConstrM runM' constr) -- return (fromConstr contr) testConstrM' :: (Read a, Data a, Read c, Read b, Data b, Data c) => [String] -> a -> (b,c) testConstrM' fieldvalues object = evalState( fromConstrM runM' (toConstr object) ) fieldvalues data Config = Config{ name :: String, age :: Int } deriving( Data, Show, Typeable, Ord, Eq, Read ) createConfig = Config "blah" 3 test = testConstrM' ["qsdfqsdf", "7"] createConfig Note that whilst I'm a total Haskell newbie (this is week 2), I've used Reflection extensively in other languages, eg wrote a fast async rpc layer over guaranteed udp for C# http://metaverse.svn.sourceforge.net/viewvc/metaverse/Trunk/Source/Metavers…, so I know more or less what I'm aiming for, just not exactly how to do it ;-)

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patch applied (generics): Added Monadic reconstruction; example of a simple deserialization.
by Oleg Kiselyov 27 Jun '07

27 Jun '07

Wed Jun 27 01:22:45 PDT 2007 oleg(a)okmij.org * Added Monadic reconstruction; example of a simple deserialization. M ./comparison/SmashA/CompanyDats.hs -1 +68 A ./comparison/SmashA/Deserialize.hs M ./comparison/SmashA/Syb4A.hs +39

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patch applied (generics): Added time measurement top-level file (forgot it earlier).
by Alexey Rodriguez Yakushev 25 Jun '07

25 Jun '07

Sat Jun 23 07:09:18 PDT 2007 patrikj(a)cs.chalmers.se * Added time measurement top-level file (forgot it earlier). A ./comparison/TestEfficiency.lhs

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patch applied (generics): Uniplate was missing from the list of approaches to test
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 09:13:59 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * Uniplate was missing from the list of approaches to test M ./comparison/test.hs -1 +1

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patch applied (generics): README
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 08:36:16 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * README M ./comparison/README -4 +10

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patch applied (generics): Cannot give instances for NGRose
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 08:33:40 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * Cannot give instances for NGRose M ./comparison/SYB1_2/GEq.lhs -1 +7

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patch applied (generics): Added nested grose trees
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 08:27:32 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * Added nested grose trees M ./comparison/LIGD/GEq.lhs -1 +7 A ./comparison/LIGD/NGRoseReps.hs A ./comparison/NGRoseDatatype.hs M ./comparison/TestFoldTreeSalary.lhs +5 A ./comparison/TestGEqNGRose.exp A ./comparison/TestGEqNGRose.lhs M ./comparison/test.hs -1 +2

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patch applied (generics): added GRose type rep for EMGM
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 04:15:17 PDT 2007 agerdes(a)mac.com * added GRose type rep for EMGM A ./comparison/EMGM/GRoseReps.hs

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patch applied (generics): Made test driver more user friendly
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 07:14:50 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * Made test driver more user friendly M ./comparison/test.hs -13 +34

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patch applied (generics): Split TestFoldTree to test traversing of a term independently from ad-hoc defs. . Also removed TestEfficiency from test
by Alexey Rodriguez Yakushev 21 Jun '07

21 Jun '07

Thu Jun 21 07:12:56 PDT 2007 Alexey Rodriguez <alexey(a)cs.uu.nl> * Split TestFoldTree to test traversing of a term independently from ad-hoc defs. . Also removed TestEfficiency from test M ./comparison/TestFoldTree.exp -1 +1 M ./comparison/TestFoldTree.lhs -2 +10 A ./comparison/TestFoldTreeSalary.exp A ./comparison/TestFoldTreeSalary.lhs M ./comparison/test.hs -2 +3

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