On Tue, Nov 1, 2011 at 5:42 PM, Magicloud Magiclouds wrote:

Hi,  I have code as following, to make a toDocument function (using Data.Bsin.=:) for a data structure.

bson :: DecsQ -> DecsQ bson decsq = do  decs <- decsq  let datad = head decs      DataD _ _ _ cons _ = datad      to = mkName "toDocument"      from = mkName "fromDocument"  fund <- mapM (\con ->                 case con of                   RecC n types -> do                     let nvs = map (\(nv, _, _) ->                                     nv                                   ) types                     funD to [clause [conP n $ map varP nvs]                              (normalB $ listE $ map (\nv ->                                                       infixE (Just $ litE $ stringL $ show nv)                                                              (varE $ mkName "=:")                                                              $ Just $ appE (varE $ mkName "val")

    $ varE nv                                                     ) nvs) []]               ) cons  return (datad : fund)

 Testing code is as:

data T = T { a :: Int           , b :: Char }

*TH> runQ (bson [d|data T = T {a :: Int, b :: Char}|])

[DataD [] T_0 [] [RecC T_1 [(a_2,NotStrict,ConT GHC.Types.Int),(b_3,NotStrict,ConT GHC.Types.Char)]] [],FunD toDocument [Clause [ConP T_1 [VarP a_2,VarP b_3]] (NormalB (ListE [InfixE (Just (LitE (StringL "a_2"))) (VarE =:) (Just (AppE (VarE val) (VarE a_2))),InfixE (Just (LitE (StringL "b_3"))) (VarE =:) (Just (AppE (VarE val) (VarE b_3)))])) []]]

 So you see that, it changed the name from T/a/b to T_0/T_1/a_2/b_3. Why is that? I did not have code to modify original data declaration. -- 竹密岂妨流水过 山高哪阻野云飞

Here is the code it actually generated: test.hs:1:1: Splicing declarations bson [d| data T = T {a :: Int, b :: String} |] ======> test.hs:(7,3)-(8,38) data T_a1XY = T_a1XZ {a_a1Y0 :: Int, b_a1Y1 :: String} toName (T_a1XZ a_a1Y0 b_a1Y1) = [("a_1627397516" =: a_a1Y0), ("b_1627397517" =: b_a1Y1)] How to avoid the name changing? -- 竹密岂妨流水过 山高哪阻野云飞