| Copyright | (c) 2012--2014 The University of Kansas |
|---|---|
| License | BSD3 |
| Maintainer | Neil Sculthorpe <neil@ittc.ku.edu> |
| Stability | beta |
| Portability | ghc |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Language.KURE.Path
Description
This module provides several Path abstractions, used for denoting a path through the tree.
- type Path crumb = [crumb]
- newtype SnocPath crumb = SnocPath [crumb]
- class ExtendPath c crumb | c -> crumb where
- (@@) :: c -> crumb -> c
- snocPathToPath :: SnocPath crumb -> Path crumb
- pathToSnocPath :: Path crumb -> SnocPath crumb
- singletonSnocPath :: crumb -> SnocPath crumb
- lastCrumb :: SnocPath crumb -> Maybe crumb
- type LocalPath = SnocPath
- type AbsolutePath = SnocPath
- class ReadPath c crumb | c -> crumb where
- absPath :: c -> AbsolutePath crumb
- lastCrumbT :: (ReadPath c crumb, Monad m) => Transform c m a crumb
- absPathT :: (ReadPath c crumb, Monad m) => Transform c m a (AbsolutePath crumb)
Paths
A crumb is a value that denotes which child node to descended into.
That is, a path through a tree is specified by a "trail of breadcrumbs".
For example, if the children are numbered, Int could be used as the crumb type.
SnocPath is useful for recording where you have been, as it is cheap to keep adding to the end of the list as you travel further.
Path is useful for recording where you intend to go, as you'll need to access it in order.
Relative Paths
type Path crumb = [crumb] Source
A Path is just a list.
The intent is that a path represents a route through the tree from an arbitrary node.
Snoc Paths
class ExtendPath c crumb | c -> crumb where Source
A class of things that can be extended by crumbs.
Typically, c is a context type.
The typical use is to extend an AbsolutePath stored in the context (during tree traversal).
Note however, that if an AbsolutePath is not stored in the context, an instance can still be declared with ('' crumb) as an identity operation.
Instances
| ExtendPath (SnocPath crumb) crumb | Any |
| (ExtendPath c crumb, ExtendPath e crumb) => ExtendPath (ExtendContext c e) crumb | Both components of the context are updated with the crumb. |
singletonSnocPath :: crumb -> SnocPath crumb Source
Absolute and Local Paths
type AbsolutePath = SnocPath Source
A SnocPath from the root.
class ReadPath c crumb | c -> crumb where Source
A class for contexts that store the current AbsolutePath, allowing transformations to depend upon it.
Instances
| ReadPath (AbsolutePath crumb) crumb | The simplest instance of |