uniplate-1.6.12: Help writing simple, concise and fast generic operations.

Safe Haskell | None
Language | Haskell98

Data.Generics.Uniplate.Typeable

Contents

- The Class
- The Combinators

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

Synopsis

- module Data.Generics.Uniplate.Operations
- module Data.Typeable
- class PlateAll from to where
  - plateAll :: from -> Type from to
- plate :: from -> Type from to
- (|+) :: (Typeable item, Typeable to, PlateAll item to) => Type (item -> from) to -> item -> Type from to
- (|-) :: Type (item -> from) to -> item -> Type from to
- plateProject :: (Typeable item, Typeable to, PlateAll item to) => (from -> item) -> (item -> from) -> from -> Type from to

# Documentation

module Data.Generics.Uniplate.Operations

module Data.Typeable

# The Class

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 `|+`, `|-`.

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 |

# The Combinators

plate :: from -> Type from to

The main combinator used to start the chain.

(|+) :: (Typeable item, Typeable to, PlateAll item to) => Type (item -> from) to -> item -> Type from to

The field to the right may contain the target.

(|-) :: 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.

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