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Data.Generics.Uniplate.Direct |
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Description |
This module supplies a method for writing Uniplate and Biplate instances.
This moulde gives the highest performance, but requires many instance definitions. The
instances can be generated using Derive: http://community.haskell.org/~ndm/derive/.
To take an example:
data Expr = Var Int | Pos Expr String | Neg Expr | Add Expr Expr
data Stmt = Seq [Stmt] | Sel [Expr] | Let String Expr
instance Uniplate Expr where
uniplate (Var x ) = plate Var |- x
uniplate (Pos x y) = plate Pos |* x |- y
uniplate (Neg x ) = plate Neg |* x
uniplate (Add x y) = plate Add |* x |* y
instance Biplate Expr Expr where
biplate = plateSelf
instance Uniplate Stmt where
uniplate (Seq x ) = plate Seq ||* x
uniplate (Sel x ) = plate Sel ||+ x
uniplate (Let x y) = plate Let |- x |- y
instance Biplate Stmt Stmt where
biplate = plateSelf
instance Biplate Stmt Expr where
biplate (Seq x ) = plate Seq ||+ x
biplate (Sel x ) = plate Sel ||* x
biplate (Let x y) = plate Let |- 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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The Combinators
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plate :: from -> Type from to | Source |
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The main combinator used to start the chain.
The following rule can be used for optimisation:
plate Ctor |- x == plate (Ctor x)
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plateSelf :: to -> Type to to | Source |
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Used for Biplate definitions where both types are the same.
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(|+) :: Biplate item to => Type (item -> from) to -> item -> Type from to | Source |
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The field to the right may contain the target.
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(|-) :: Type (item -> from) to -> item -> Type from to | Source |
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The field to the right does not contain the target.
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(|*) :: Type (to -> from) to -> to -> Type from to | Source |
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The field to the right is the target.
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(||+) :: Biplate item to => Type ([item] -> from) to -> [item] -> Type from to | Source |
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The field to the right is a list of types which may contain the target
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(||*) :: Type ([to] -> from) to -> [to] -> Type from to | Source |
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The field to the right is a list of the type of the target
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plateProject :: Biplate item to => (from -> item) -> (item -> from) -> from -> Type from to | Source |
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Write an instance in terms of a projection/injection pair. Usually used to define instances
for abstract containers such as Map:
instance Biplate (Map.Map [Char] Int) Int where
biplate = plateProject Map.toAscList Map.fromDistinctAscList
Because we know that Uniplate operations will not change the keys,
we can use the fromDistictAscList function to reconstruct it.
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Produced by Haddock version 2.4.2 |