| Copyright | (C) 2012-2014 Edward Kmett |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | Trustworthy |
| Language | Haskell98 |
Control.Lens.Internal.Level
Contents
Description
This module provides implementation details of the combinators in
Control.Lens.Level, which provides for the breadth-first Traversal of
an arbitrary Traversal.
Levels
This data type represents a path-compressed copy of one level of a source data structure. We can safely use path-compression because we know the depth of the tree.
Path compression is performed by viewing a Level as a PATRICIA trie of the
paths into the structure to leaves at a given depth, similar in many ways
to a IntMap, but unlike a regular PATRICIA trie we do not need
to store the mask bits merely the depth of the fork.
One invariant of this structure is that underneath a Two node you will not
find any Zero nodes, so Zero can only occur at the root.
Constructors
| Deepening | |
Fields
| |
deepening :: i -> a -> Deepening i a Source
Generate the leaf of a given Deepening based on whether or not we're at the correct depth.
This is an illegal Applicative used to replace the contents of a list of consecutive Level values
representing each layer of a structure into the original shape that they were derived from.
Attempting to Flow something back into a shape other than the one it was taken from will fail.
Instances
| Functor (Flows i b) | |
| Applicative (Flows i b) | This is an illegal |
| Apply (Flows i b) |