    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.Generics.Instances
    -- Copyright   :  (c) The University of Glasgow, CWI 2001--2004
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  experimental
    -- Portability :  non-portable (uses Data.Generics.Basics)
    --
    -- \"Scrap your boilerplate\" --- Generic programming in Haskell
    -- See <http://www.cs.vu.nl/boilerplate/>. The present module
    -- instantiates the class Data for Prelude-like datatypes.
    -- (This module does not export anything. It really just defines instances.)
    --
    -----------------------------------------------------------------------------

    module Data.Generics.Instances where

    ------------------------------------------------------------------------------

    #ifdef __HADDOCK__
    import Prelude
    #endif

    import Data.Generics.Basics

    import Data.Typeable
    import Data.Int              -- So we can give Data instance for Int8, ...
    import Data.Word             -- So we can give Data instance for Word8, ...
    import GHC.Real( Ratio(..) ) -- So we can give Data instance for Ratio
    import GHC.IOBase            -- So we can give Data instance for IO, Handle
    import GHC.Ptr               -- So we can give Data instance for Ptr
    import GHC.ForeignPtr        -- So we can give Data instance for ForeignPtr
    import GHC.Stable            -- So we can give Data instance for StablePtr
    import GHC.ST                -- So we can give Data instance for ST
    import GHC.Conc              -- So we can give Data instance for MVar & Co.
    import GHC.Arr               -- So we can give Data instance for Array

    #include "Typeable.h"

    ------------------------------------------------------------------------------
    --
    --      Instances of the Data class for Prelude-like types.
    --      We define top-level definitions for representations.
    --
    ------------------------------------------------------------------------------

    falseConstr  = mkConstr boolDataType "False" [] Prefix
    trueConstr   = mkConstr boolDataType "True"  [] Prefix
    boolDataType = mkDataType "Prelude.Bool" [falseConstr,trueConstr]

    instance Data Bool where
      toConstr False = falseConstr
      toConstr True  = trueConstr
      gunfold k z c  = case constrIndex c of
                         1 -> z False
                         2 -> z True
                         _ -> error "gunfold"
      dataTypeOf _ = boolDataType

    ------------------------------------------------------------------------------

    charType = mkStringType "Prelude.Char"

    instance Data Char where
      toConstr x = mkStringConstr charType [x]
      gunfold k z c = case constrRep c of
                        (StringConstr [x]) -> z x
                        _ -> error "gunfold"
      dataTypeOf _ = charType

    ------------------------------------------------------------------------------

    floatType = mkFloatType "Prelude.Float"

    instance Data Float where
      toConstr x = mkFloatConstr floatType (realToFrac x)
      gunfold k z c = case constrRep c of
                        (FloatConstr x) -> z (realToFrac x)
                        _ -> error "gunfold"
      dataTypeOf _ = floatType

    ------------------------------------------------------------------------------

    doubleType = mkFloatType "Prelude.Double"

    instance Data Double where
      toConstr = mkFloatConstr floatType
      gunfold k z c = case constrRep c of
                        (FloatConstr x) -> z x
                        _ -> error "gunfold"
      dataTypeOf _ = doubleType

    ------------------------------------------------------------------------------

    intType = mkIntType "Prelude.Int"

    instance Data Int where
      toConstr x = mkIntConstr intType (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = intType

    ------------------------------------------------------------------------------

    integerType = mkIntType "Prelude.Integer"

    instance Data Integer where
      toConstr = mkIntConstr integerType
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z x
                        _ -> error "gunfold"
      dataTypeOf _ = integerType

    ------------------------------------------------------------------------------

    int8Type = mkIntType "Data.Int.Int8"

    instance Data Int8 where
      toConstr x = mkIntConstr int8Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = int8Type

    ------------------------------------------------------------------------------

    int16Type = mkIntType "Data.Int.Int16"

    instance Data Int16 where
      toConstr x = mkIntConstr int16Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = int16Type

    ------------------------------------------------------------------------------

    int32Type = mkIntType "Data.Int.Int32"

    instance Data Int32 where
      toConstr x = mkIntConstr int32Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = int32Type

    ------------------------------------------------------------------------------

    int64Type = mkIntType "Data.Int.Int64"

    instance Data Int64 where
      toConstr x = mkIntConstr int64Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = int64Type

    ------------------------------------------------------------------------------

    wordType = mkIntType "Data.Word.Word"

    instance Data Word where
      toConstr x = mkIntConstr wordType (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = wordType

    ------------------------------------------------------------------------------

    word8Type = mkIntType "Data.Word.Word8"

    instance Data Word8 where
      toConstr x = mkIntConstr word8Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = word8Type

    ------------------------------------------------------------------------------

    word16Type = mkIntType "Data.Word.Word16"

    instance Data Word16 where
      toConstr x = mkIntConstr word16Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = word16Type

    ------------------------------------------------------------------------------

    word32Type = mkIntType "Data.Word.Word32"

    instance Data Word32 where
      toConstr x = mkIntConstr word32Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = word32Type

    ------------------------------------------------------------------------------

    word64Type = mkIntType "Data.Word.Word64"

    instance Data Word64 where
      toConstr x = mkIntConstr word64Type (fromIntegral x)
      gunfold k z c = case constrRep c of
                        (IntConstr x) -> z (fromIntegral x)
                        _ -> error "gunfold"
      dataTypeOf _ = word64Type

    ------------------------------------------------------------------------------

    ratioConstr = mkConstr ratioDataType ":%" [] Infix
    ratioDataType = mkDataType "GHC.Real.Ratio" [ratioConstr]

    instance (Data a, Integral a) => Data (Ratio a) where
      toConstr _ = ratioConstr
      gunfold k z c | constrIndex c == 1 = k (k (z (:%)))
      gunfold _ _ _ = error "gunfold"
      dataTypeOf _  = ratioDataType

    ------------------------------------------------------------------------------

    nilConstr    = mkConstr listDataType "[]" [] Prefix
    consConstr   = mkConstr listDataType "(:)" [] Infix
    listDataType = mkDataType "Prelude.[]" [nilConstr,consConstr]

    instance Data a => Data [a] where
      gfoldl f z []     = z []
      gfoldl f z (x:xs) = z (:) `f` x `f` xs
      toConstr []    = nilConstr
      toConstr (_:_) = consConstr
      gunfold k z c = case constrIndex c of
                        1 -> z []
                        2 -> k (k (z (:)))
                        _ -> error "gunfold"
      dataTypeOf _ = listDataType
      dataCast1 f  = gcast1 f

    --
    -- The gmaps are given as an illustration.
    -- This shows that the gmaps for lists are different from list maps.
    --
      gmapT  f   []     = []
      gmapT  f   (x:xs) = (f x:f xs)
      gmapQ  f   []     = []
      gmapQ  f   (x:xs) = [f x,f xs]
      gmapM  f   []     = return []
      gmapM  f   (x:xs) = f x >>= \x' -> f xs >>= \xs' -> return (x':xs')

    ------------------------------------------------------------------------------

    nothingConstr = mkConstr maybeDataType "Nothing" [] Prefix
    justConstr    = mkConstr maybeDataType "Just"    [] Prefix
    maybeDataType = mkDataType "Prelude.Maybe" [nothingConstr,justConstr]

    instance Data a => Data (Maybe a) where
      gfoldl f z Nothing  = z Nothing
      gfoldl f z (Just x) = z Just `f` x
      toConstr Nothing  = nothingConstr
      toConstr (Just _) = justConstr
      gunfold k z c = case constrIndex c of
                        1 -> z Nothing
                        2 -> k (z Just)
                        _ -> error "gunfold"
      dataTypeOf _ = maybeDataType
      dataCast1 f  = gcast1 f

    ------------------------------------------------------------------------------

    ltConstr         = mkConstr orderingDataType "LT" [] Prefix
    eqConstr         = mkConstr orderingDataType "EQ" [] Prefix
    gtConstr         = mkConstr orderingDataType "GT" [] Prefix
    orderingDataType = mkDataType "Prelude.Ordering" [ltConstr,eqConstr,gtConstr]

    instance Data Ordering where
      gfoldl f z LT  = z LT
      gfoldl f z EQ  = z EQ
      gfoldl f z GT  = z GT
      toConstr LT  = ltConstr
      toConstr EQ  = eqConstr
      toConstr GT  = gtConstr
      gunfold k z c = case constrIndex c of
                        1 -> z LT
                        2 -> z EQ
                        3 -> z GT
                        _ -> error "gunfold"
      dataTypeOf _ = orderingDataType

    ------------------------------------------------------------------------------

    leftConstr     = mkConstr eitherDataType "Left"  [] Prefix
    rightConstr    = mkConstr eitherDataType "Right" [] Prefix
    eitherDataType = mkDataType "Prelude.Either" [leftConstr,rightConstr]

    instance (Data a, Data b) => Data (Either a b) where
      gfoldl f z (Left a)   = z Left  `f` a
      gfoldl f z (Right a)  = z Right `f` a
      toConstr (Left _)  = leftConstr
      toConstr (Right _) = rightConstr
      gunfold k z c = case constrIndex c of
                        1 -> k (z Left)
                        2 -> k (z Right)
                        _ -> error "gunfold"
      dataTypeOf _ = eitherDataType
      dataCast2 f  = gcast2 f

    ------------------------------------------------------------------------------

    --
    -- A last resort for functions
    --

    instance (Data a, Data b) => Data (a -> b) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "Prelude.(->)"
      dataCast2 f  = gcast2 f

    ------------------------------------------------------------------------------

    tuple0Constr = mkConstr tuple0DataType "()" [] Prefix
    tuple0DataType = mkDataType "Prelude.()" [tuple0Constr]

    instance Data () where
      toConstr ()   = tuple0Constr
      gunfold k z c | constrIndex c == 1 = z ()
      gunfold _ _ _ = error "gunfold"
      dataTypeOf _  = tuple0DataType

    ------------------------------------------------------------------------------

    tuple2Constr = mkConstr tuple2DataType "(,)" [] Infix
    tuple2DataType = mkDataType "Prelude.(,)" [tuple2Constr]

    instance (Data a, Data b) => Data (a,b) where
      gfoldl f z (a,b) = z (,) `f` a `f` b
      toConstr (a,b) = tuple2Constr
      gunfold k z c | constrIndex c == 1 = k (k (z (,)))
      gunfold _ _ _ = error "gunfold"
      dataTypeOf _  = tuple2DataType
      dataCast2 f   = gcast2 f

    ------------------------------------------------------------------------------

    tuple3Constr = mkConstr tuple3DataType "(,,)" [] Infix
    tuple3DataType = mkDataType "Prelude.(,)" [tuple3Constr]

    instance (Data a, Data b, Data c) => Data (a,b,c) where
      gfoldl f z (a,b,c) = z (,,) `f` a `f` b `f` c
      toConstr (a,b,c) = tuple3Constr
      gunfold k z c | constrIndex c == 1 = k (k (k (z (,,))))
      gunfold _ _ _ = error "gunfold"
      dataTypeOf _  = tuple3DataType

    ------------------------------------------------------------------------------

    tuple4Constr = mkConstr tuple4DataType "(,,,)" [] Infix
    tuple4DataType = mkDataType "Prelude.(,,,)" [tuple4Constr]

    instance (Data a, Data b, Data c, Data d)
             => Data (a,b,c,d) where
      gfoldl f z (a,b,c,d) = z (,,,) `f` a `f` b `f` c `f` d
      toConstr (a,b,c,d) = tuple4Constr
      gunfold k z c = case constrIndex c of
                        1 -> k (k (k (k (z (,,,)))))
                        _ -> error "gunfold"
      dataTypeOf _ = tuple4DataType

    ------------------------------------------------------------------------------

    tuple5Constr = mkConstr tuple5DataType "(,,,,)" [] Infix
    tuple5DataType = mkDataType "Prelude.(,,,,)" [tuple5Constr]

    instance (Data a, Data b, Data c, Data d, Data e)
             => Data (a,b,c,d,e) where
      gfoldl f z (a,b,c,d,e) = z (,,,,) `f` a `f` b `f` c `f` d `f` e
      toConstr (a,b,c,d,e) = tuple5Constr
      gunfold k z c = case constrIndex c of
                        1 -> k (k (k (k (k (z (,,,,))))))
                        _ -> error "gunfold"
      dataTypeOf _ = tuple5DataType

    ------------------------------------------------------------------------------

    tuple6Constr = mkConstr tuple6DataType "(,,,,,)" [] Infix
    tuple6DataType = mkDataType "Prelude.(,,,,,)" [tuple6Constr]

    instance (Data a, Data b, Data c, Data d, Data e, Data f)
             => Data (a,b,c,d,e,f) where
      gfoldl f z (a,b,c,d,e,f') = z (,,,,,) `f` a `f` b `f` c `f` d `f` e `f` f'
      toConstr (a,b,c,d,e,f) = tuple6Constr
      gunfold k z c = case constrIndex c of
                        1 -> k (k (k (k (k (k (z (,,,,,)))))))
                        _ -> error "gunfold"
      dataTypeOf _ = tuple6DataType

    ------------------------------------------------------------------------------

    tuple7Constr = mkConstr tuple7DataType "(,,,,,,)" [] Infix
    tuple7DataType = mkDataType "Prelude.(,,,,,,)" [tuple7Constr]

    instance (Data a, Data b, Data c, Data d, Data e, Data f, Data g)
             => Data (a,b,c,d,e,f,g) where
      gfoldl f z (a,b,c,d,e,f',g) =
        z (,,,,,,) `f` a `f` b `f` c `f` d `f` e `f` f' `f` g
      toConstr  (a,b,c,d,e,f,g) = tuple7Constr
      gunfold k z c = case constrIndex c of
                        1 -> k (k (k (k (k (k (k (z (,,,,,,))))))))
                        _ -> error "gunfold"
      dataTypeOf _ = tuple7DataType

    ------------------------------------------------------------------------------

    instance Data TypeRep where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "Data.Typeable.TypeRep"

    ------------------------------------------------------------------------------

    instance Data TyCon where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "Data.Typeable.TyCon"

    ------------------------------------------------------------------------------

    INSTANCE_TYPEABLE0(DataType,dataTypeTc,"DataType")

    instance Data DataType where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "Data.Generics.Basics.DataType"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (IO a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.IOBase.IO"

    ------------------------------------------------------------------------------

    instance Data Handle where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.IOBase.Handle"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (Ptr a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Ptr.Ptr"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (StablePtr a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Stable.StablePtr"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (IORef a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.IOBase.IORef"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (ForeignPtr a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.ForeignPtr.ForeignPtr"

    ------------------------------------------------------------------------------

    instance (Typeable s, Typeable a) => Data (ST s a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.ST.ST"

    ------------------------------------------------------------------------------

    instance Data ThreadId where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Conc.ThreadId"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (TVar a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Conc.TVar"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (MVar a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Conc.MVar"

    ------------------------------------------------------------------------------

    instance Typeable a => Data (STM a) where
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "GHC.Conc.STM"

    ------------------------------------------------------------------------------
    -- The Data instance for Array preserves data abstraction at the cost of inefficiency.
    -- We omit reflection services for the sake of data abstraction.
    instance (Typeable a, Data b, Ix a) => Data (Array a b)
     where
      gfoldl f z a = z (listArray (bounds a)) `f` (elems a)
      toConstr _   = error "toConstr"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNorepType "Data.Array.Array"