Copyright | (c) Andrew Seniuk, 2014 |
---|---|

License | BSD-style (see the LICENSE file) |

Maintainer | rasfar@gmail.com |

Stability | experimental |

Portability | non-portable (uses Data.Generics.Basics) |

Safe Haskell | None |

Language | Haskell2010 |

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.

- type Homo r = Rose r
- type Hetero = Homo Dynamic
- type Bi r = Homo (Dynamic, r)
- type Shape = Homo ()
- type HomoM r = Homo (Maybe r)
- type BiM r = Bi (Maybe r)
- type Rose = Tree
- ghom :: forall r d. Data d => GenericQ r -> d -> Homo r
- ghomK :: forall r d. Data d => (r -> r -> r) -> GenericQ r -> d -> Homo r
- ghomP :: forall r s d. Data d => GenericQ Bool -> GenericQ r -> d -> Homo r
- ghomE :: forall r s d. Data d => GenericQ Bool -> GenericQ r -> GenericQ s -> d -> Homo (Either r s)
- ghomDyn :: forall d. Data d => d -> Hetero
- ghomBi :: forall r d. Data d => GenericQ r -> d -> Bi r
- unGhomDyn :: Typeable a => Hetero -> a
- unGhomBi :: Typeable a => Bi r -> a
- biToHomo :: Bi r -> Homo r
- biToHetero :: Bi r -> Hetero
- heteroToBi :: forall r d. (Data d, Typeable d, Typeable r) => r -> (d -> r) -> Hetero -> Bi r
- liftHomoM :: Homo r -> HomoM r
- liftBiM :: Bi r -> BiM r
- unliftHomoM :: r -> HomoM r -> Homo r
- unliftBiM :: r -> BiM r -> Bi r
- gempty :: forall r d. (Typeable r, Data d) => d -> BiM r
- grefine :: forall r d. (Typeable r, Data d, Typeable d) => (d -> Maybe r) -> BiM r -> BiM r
- gaccum :: forall r d. (Typeable r, Data d, Typeable d) => (r -> r -> r) -> (d -> Maybe r) -> BiM r -> BiM r
- shapeOf :: forall d. Data d => d -> Shape
- shapeOf_ :: forall d. Data d => d -> Shape
- sizeOf :: forall d. Data d => d -> Int
- symmorphic :: forall d1 d2. (Data d1, Data d2) => d1 -> d2 -> Bool
- (~~) :: forall d1 d2. (Data d1, Data d2) => d1 -> d2 -> Bool
- weightedShapeOf :: forall d. Data d => d -> Homo Int
- weightedShapeOf_ :: forall d. Data d => d -> Homo Int
- weightedRose :: Rose r -> Rose (r, Int)
- weightedRoseJust :: Rose (Maybe r) -> Rose (Maybe r, Int)
- sizeOfRose :: Rose a -> Int
- zipRose :: Rose r -> Rose s -> Rose (r, s)
- unzipRose :: Rose (r, s) -> (Rose r, Rose s)
- zipBi :: Bi r -> Bi s -> Bi (r, s)
- unzipBi :: Bi (r, s) -> (Bi r, Bi s)
- zip :: (Applicative f, Functor f) => (f a, f b) -> f (a, b)
- unzip :: Functor f => f (a, b) -> (f a, f b)
- showHomo :: Show r => Rose r -> String
- showHomoWhen :: Show r => (r -> Bool) -> Rose r -> String
- showHomoM :: Show r => Rose (Maybe r) -> String
- showAsParens :: Homo r -> String
- showAsParensBool :: Homo Bool -> String
- showAsParensEnriched :: Show r => Homo r -> String
- showAsParensEnrichedWhen :: Show r => (r -> Bool) -> Homo r -> String
- showAsParensEnrichedM :: Show r => HomoM r -> String
- showDyn :: Dynamic -> String
- showHetero :: Hetero -> String
- showBi :: Show r => Bi r -> String
- data Tree a :: * -> * = Node a (Forest a)
- type Forest a = [Tree a]

# Types

# Rose Tree Type

# 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)`

.

ghomE :: forall r s d. Data d => GenericQ Bool -> GenericQ r -> GenericQ s -> d -> Homo (Either r s) Source

Like `ghom`

, but also filter branches using a generic predicate,
retaining the stop nodes and summarising their branches in
`Right`

values; default values are placed in the non-stop, `Left`

nodes.
You can fmap your own function `(s -> r)`

to the result, then collapse
from

to `Either`

r r`r`

in the obvious way. (The function `ghomP`

is
probably sufficient in most cases.)

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

Uses Data.Dynamic to support mutiple types homogeneously.
Unlike `ghom`

, this is invertible (`unGhomDyn`

).

# Inverses where possible

# 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

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

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

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

using a default `BiM`

r`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

value
returned contains `BiM`

r`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

from this. It then maps
the generic query over the source polytypic tree, the latter
being recovered from the `GenericQ`

r`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.

XXX *Still only calls error, when should throw an exception.*

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.

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

Compare two general polytypic values 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.

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

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

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.

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

.

showAsParens :: Homo r -> String Source

One-line, parentheses language representation of the shape of a

.`Homo`

r

showAsParensBool :: Homo Bool -> String Source

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

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

showHetero :: Hetero -> String Source

# Re-exported from Data.Tree

data Tree a :: * -> *

Multi-way trees, also known as *rose trees*.