uniplate-1.6.13: Help writing simple, concise and fast generic operations.

Safe Haskell | Safe-Inferred
Language | Haskell2010

Data.Generics.PlateDirect

Contents

- The Combinators

Description

Deprecated: Use Data.Generics.Uniplate.Direct instead

DEPRECATED: Use Data.Generics.Uniplate.Direct instead.

This module supplies a method for writing `Biplate` instances more easily. This module requires fewest extensions, highest performance, and most instance definitions.

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

Synopsis

- module Data.Generics.Biplate
- plate :: from -> Type from to
- plateSelf :: to -> Type to to
- (|+) :: Biplate item to => Type (item -> from) to -> item -> Type from to
- (|-) :: Type (item -> from) to -> item -> Type from to
- (|*) :: Type (to -> from) to -> to -> Type from to
- (||+) :: Biplate item to => Type ([item] -> from) to -> [item] -> Type from to
- (||*) :: Type ([to] -> from) to -> [to] -> Type from to

# Documentation

module Data.Generics.Biplate

# 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)

plateSelf :: to -> Type to to #

Used for `PlayAll` definitions where both types are the same.

(|+) :: Biplate 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.

(|*) :: Type (to -> from) to -> to -> Type from to #

The field to the right is the target.

(||+) :: Biplate item to => Type ([item] -> from) to -> [item] -> Type from to #

The field to the right is a list of types which may contain the target

(||*) :: Type ([to] -> from) to -> [to] -> Type from to #

The field to the right is a list of the type of the target