lens-4.9.1: 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

 TraversableWithIndex i (Level i) Source FoldableWithIndex i (Level i) Source FunctorWithIndex i (Level i) Source Functor (Level i) Source Foldable (Level i) Source Traversable (Level i) Source (Eq i, Eq a) => Eq (Level i a) Source (Ord i, Ord a) => Ord (Level i a) Source (Read i, Read a) => Read (Level i a) Source (Show i, Show a) => Show (Level i a) Source

newtype Deepening i a Source

This is an illegal `Monoid` used to construct a single `Level`.

Constructors

 Deepening FieldsrunDeepening :: forall r. Int -> (Level i a -> Bool -> r) -> r

Instances

 Monoid (Deepening i a) Source This is an illegal `Monoid`. Semigroup (Deepening i a) Source

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.

newtype Flows i b a Source

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.

Constructors

 Flows FieldsrunFlows :: [Level i b] -> a

Instances

 Functor (Flows i b) Source Applicative (Flows i b) Source This is an illegal `Applicative`. Apply (Flows i b) Source