 | uniplate-1.6: Help writing simple, concise and fast generic operations. | Contents | Index |
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Data.Generics.Uniplate.Typeable |
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Description |
RECOMMENDATION: Use Data.Generics.Uniplate.Data instead - it usually performs
faster (sometimes significantly so) and requires no special instance declarations.
This module supplies a method for writing Uniplate / Biplate instances. One
instance declaration is required for each data type you wish to work with. The
instances can be generated using Derive: http://community.haskell.org/~ndm/derive/.
To take an example:
data Expr = Var Int | Neg Expr | Add Expr Expr
deriving Typeable
instance (Typeable a, Uniplate a) => PlateAll Expr a where
plateAll (Var x ) = plate Var |+ x
plateAll (Neg x ) = plate Neg |+ x
plateAll (Add x y) = plate Add |+ x |+ y
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Synopsis |
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Documentation |
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module Data.Generics.Uniplate.Operations |
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module Data.Typeable |
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The Class
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class PlateAll from to where |
This class should be defined for each data type of interest.
| | Methods | plateAll :: from -> Type from to | This method should be defined using plate and |+, |-.
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| | Instances | PlateAll Bool to | | PlateAll Char to | | PlateAll Double to | | PlateAll Float to | | PlateAll Int to | | PlateAll Integer to | | PlateAll () to | | (PlateAll from to, Typeable from, Typeable to, Uniplate to) => PlateAll [from] to | | (Integral a, PlateAll a to, Typeable a, Typeable to, Uniplate to) => PlateAll (Ratio a) to | | (PlateAll from to, Typeable from, Typeable to, Uniplate to) => PlateAll (Maybe from) to | | (PlateAll a to, Typeable a, PlateAll b to, Typeable b, Typeable to, Uniplate to) => PlateAll (Either a b) to | | (PlateAll a to, Typeable a, PlateAll b to, Typeable b, Typeable to, Uniplate to) => PlateAll (a, b) to | | (PlateAll a to, Typeable a, PlateAll b to, Typeable b, PlateAll c to, Typeable c, Typeable to, Uniplate to) => PlateAll (a, b, c) to | | (PlateAll a to, Typeable a, PlateAll b to, Typeable b, PlateAll c to, Typeable c, PlateAll d to, Typeable d, Typeable to, Uniplate to) => PlateAll (a, b, c, d) to | | (PlateAll a to, Typeable a, PlateAll b to, Typeable b, PlateAll c to, Typeable c, PlateAll d to, Typeable d, PlateAll e to, Typeable e, Typeable to, Uniplate to) => PlateAll (a, b, c, d, e) to | |
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The Combinators
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plate :: from -> Type from to |
The main combinator used to start the chain.
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(|+) :: (Typeable item, Typeable to, PlateAll item to) => Type (item -> from) to -> item -> Type from to |
The field to the right may contain the target.
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(|-) :: Type (item -> from) to -> item -> Type from to |
The field to the right does not contain the target.
This can be used as either an optimisation, or more commonly for excluding
primitives such as Int.
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plateProject :: (Typeable item, Typeable to, PlateAll item to) => (from -> item) -> (item -> from) -> from -> Type from to |
Write an instance in terms of a projection/injection pair. Usually used to define instances
for abstract containers such as Map:
instance (Ord a, Typeable a, PlateAll a c, Typeable b, PlateAll b c,
Typeable c, PlateAll c c) => PlateAll (Map.Map a b) c where
plateAll = plateProject Map.toList Map.fromList
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