lens-5.0.1: Lenses, Folds and Traversals

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.

Synopsis

# Levels

data Level i a Source #

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

 Two !Word !(Level i a) !(Level i a) One i a Zero

#### Instances

Instances details