sai-shape-syb-0.2.1: Obtain homogeneous values from arbitrary values, tramsforming or culling data

Copyright(c) Andrew Seniuk, 2014
LicenseBSD-style (see the LICENSE file)
Maintainerrasfar@gmail.com
Stabilityexperimental
Portabilitynon-portable (uses Data.Generics.Basics)
Safe HaskellNone
LanguageHaskell2010

SAI.Data.Generics.Shape.SYB

Contents

Description

This package provides SYB shape support: generic mapping to homogeneous types, and related features. Complements existing Uniplate and TH shape libraries. See http://www.fremissant.net/shape-syb for more information.

The present module provides the main types and functions.

Synopsis

Types

type Homo r = Rose r Source

type Hetero = Homo Dynamic Source

type Bi r = Homo (Dynamic, r) Source

type Shape = Homo () Source

type HomoM r = Homo (Maybe r) Source

type BiM r = Bi (Maybe r) Source

Rose Tree Type

type Rose = Tree Source

From Data.Tree we have, essentially

data Tree r = Node r [Tree r]

Homomorphisms

ghom :: forall r d. Data d => GenericQ r -> d -> Homo r Source

Map an arbitrary data constructor application expression to a homogeneous representation preserving structure. This is a one-way trip; what value information is preserved depends on the mapping function you provide. Use ghomDyn or ghomBi if you need to be able to recover the original, heterogeneous data.

ghomK :: forall r d. Data d => (r -> r -> r) -> GenericQ r -> d -> Homo r Source

Like ghom, but use a custom combining function, instead of the default (\r _->r).

ghomDyn :: forall d. Data d => d -> Hetero Source

Uses Data.Dynamic to support mutiple types homogeneously. Unlike ghom, this is invertible (unGhomDyn).

ghomBi :: forall r d. Data d => GenericQ r -> d -> Bi r Source

ghomBi f x = zipRose (ghomDyn x) (ghom f x)

Unlike ghom, you can recover the original, polytypic term (unGhomBi).

Inverses where possible

unGhomDyn :: Typeable a => Hetero -> a Source

unGhomBi :: Typeable a => Bi r -> a Source

Conversions

These conversion functions should obey at least the following laws.

ghom f = biToHomo . ghomBi f
biToHetero . ghomBi g = biToHetero . ghomBi f
ghomBi f = heteroToBi f . ghomDyn
ghomBi g = heteroToBi g . biToHetero . ghomBi f

biToHomo :: Bi r -> Homo r Source

Drops the Dynamic component.

biToHetero :: Bi r -> Hetero Source

Drops the homogeneous component (type r).

heteroToBi :: forall r d. (Data d, Typeable d, Typeable r) => r -> (d -> r) -> Hetero -> Bi r Source

Conversions concerning lifted types

liftHomoM :: Homo r -> HomoM r Source

Conversion from Homo to HomoM by wrapping values in Just.

liftBiM :: Bi r -> BiM r Source

Analogous to liftHomoM.

unliftHomoM :: r -> HomoM r -> Homo r Source

Sometimes it makes sense to replace the Nothing nodes with a default value in type r.

The best default value will often be some function of the filtered, Just items.

unliftHomoM = fmap . flip maybe id

Lineal ordering is preserved among Just nodes.

unliftBiM :: r -> BiM r -> Bi r Source

Analogous to unliftHomoM.

Progressive refinement and accumulation

gempty :: forall r d. (Typeable r, Data d) => d -> BiM r Source

Sets up a BiM r using a default GenericQ which assigns all values to Nothing.

Use an expression type signature at the call site, to constrain the type r (the usual trick)

 ( gempty x :: BiM ( Int , Data.IntMap Text , [Float] ) )

so your choice type r is a triple, but the BiM r value returned contains Nothing at every node. This prepares it for refinement and accumulation.

grefine :: forall r d. (Typeable r, Data d, Typeable d) => (d -> Maybe r) -> BiM r -> BiM r Source

Given a monomorphic function you provide, returning r, automatically makes a GenericQ r from this. It then maps the generic query over the source polytypic tree, the latter being recovered from the Dynamic component of the BiM.

The target is updated with write-once semantics enforced; that is to say, grefine will throw an exception if it finds a Just already present at any place in the result tree that it would update.

gaccum :: forall r d. (Typeable r, Data d, Typeable d) => (r -> r -> r) -> (d -> Maybe r) -> BiM r -> BiM r Source

Like grefine, but rather than throw exception, it takes a combining function argument to cope with that situation.

For convenience

shapeOf :: forall d. Data d => d -> Shape Source

Trivial homomorphism that discards all value information.

sizeOf :: forall d. Data d => d -> Int Source

Generic number of nodes in a polytypic term.

symmorphic :: forall d1 d2. (Data d1, Data d2) => d1 -> d2 -> Bool Source

Compare two rose trees for shape equality.

(~~) :: forall d1 d2. (Data d1, Data d2) => d1 -> d2 -> Bool Source

Operator synonymous with symmorphic.

weightedShapeOf :: forall d. Data d => d -> Homo Int Source

Weight of a node is defined as the number of descendants, plus 1.

weightedRose :: Rose r -> Rose (r, Int) Source

weightedRoseJust :: Rose (Maybe r) -> Rose (Maybe r, Int) Source

Produce a zipped rose tree, where the second component at a node is the number of non-Nothing (i.e. Just) descendants, plus one for itself if it is Just.

sizeOfRose :: Rose a -> Int Source

Number of nodes in a rose tree.

zipRose :: Rose r -> Rose s -> Rose (r, s) Source

Combine two rose trees with identical shape, by tupling their values.

unzipRose :: Rose (r, s) -> (Rose r, Rose s) Source

Inverse of zipRose (up to Currying).

zipBi :: Bi r -> Bi s -> Bi (r, s) Source

Zip two Bis. It is the caller's responsibility to assure that the Dynamic component is the same in both arguments (in addition to assuring that the shapes are compatible).

unzipBi :: Bi (r, s) -> (Bi r, Bi s) Source

zip :: (Applicative f, Functor f) => (f a, f b) -> f (a, b) Source

unzip :: Functor f => f (a, b) -> (f a, f b) Source

Showing values

Pretty-printing of rose trees, including compact representations. Also, show functions for a subset of Dynamic values, which show the value and not just <<type>>.

showHomo :: Show r => Rose r -> String Source

showHomoM :: Show r => Rose (Maybe r) -> String Source

showAsParens :: Homo r -> String Source

showAsParensBool :: Homo Bool -> String Source

showAsParensEnriched :: Show r => Homo r -> String Source

showAsParensEnrichedM :: Show r => HomoM r -> String Source

showDyn :: Dynamic -> String Source

showHetero :: Hetero -> String Source

showBi :: Show r => Bi r -> String Source

Re-exported from Data.Tree

data Tree a :: * -> *

Multi-way trees, also known as rose trees.

Constructors

Node a (Forest a) 

Instances

Monad Tree 
Functor Tree 
Applicative Tree 
Foldable Tree 
Traversable Tree 
Eq a => Eq (Tree a) 
Data a => Data (Tree a) 
Read a => Read (Tree a) 
Show a => Show (Tree a) 
NFData a => NFData (Tree a) 
Typeable (* -> *) Tree 

type Forest a = [Tree a]