Data.Generics.PlateTypeable

This module supplies a method for writing Biplate instances more easily.

To take an example:

 data Expr = Var Int | Neg Expr | Add Expr Expr

 instance Typeable Expr where ...

 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

 instance Uniplate Expr where
   uniplate = uniplateAll

Documentation

module Data.Generics.Biplate

module Data.Typeable

The Class

class PlateAll from to where

This class represents going from the container type to the target.

This class should only be constructed with plate, |+ and |-

Methods

plateAll :: from -> Type from to

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

(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

uniplateAll :: PlateAll a b => a -> (Str b, Str b -> a)

This function is used to write a Uniplate instance from a PlateAll one

The Combinators

plate :: from -> Type from to

The main combinator used to start the chain.

The following rule can be used for optimisation:

 plate Ctor |- x == plate (Ctor x)

(|+) :: (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.