lens-3.9.0.2: Lenses, Folds and Traversals

Portability | non-portable
Stability | provisional
Maintainer | Edward Kmett <ekmett@gmail.com>
Safe Haskell | Trustworthy

Data.Vector.Generic.Lens

Contents

- Isomorphisms
- Lenses
- Traversal of individual indices

Description

This module provides lenses and traversals for working with generic vectors.

Synopsis

- toVectorOf :: Vector v a => Getting (Endo [a]) s a -> s -> v a
- forced :: Vector v a => Iso' (v a) (v a)
- vector :: Vector v a => Iso' [a] (v a)
- asStream :: Vector v a => Iso' (v a) (Stream a)
- asStreamR :: Vector v a => Iso' (v a) (Stream a)
- cloned :: Vector v a => Iso' (v a) (New v a)
- sliced :: Vector v a => Int -> Int -> Lens' (v a) (v a)
- ordinals :: Vector v a => [Int] -> IndexedTraversal' Int (v a) a

# Documentation

toVectorOf :: Vector v a => Getting (Endo [a]) s a -> s -> v a

Similar to `toListOf`, but returning a `Vector`.

    >>> toVectorOf both (8,15) :: Vector.Vector Int
    fromList [8,15]

# Isomorphisms

forced :: Vector v a => Iso' (v a) (v a)

Convert a `Vector` to a version that doesn't retain any extra memory.

vector :: Vector v a => Iso' [a] (v a)

Convert a list to a `Vector` (or back.)

    >>> [1,2,3] ^. vector :: Vector.Vector Int
    fromList [1,2,3]

    >>> Vector.fromList [0,8,15] ^. from vector
    [0,8,15]

asStream :: Vector v a => Iso' (v a) (Stream a)

Convert a `Vector` to a finite `Stream` (or back.)

asStreamR :: Vector v a => Iso' (v a) (Stream a)

Convert a `Vector` to a finite `Stream` from right to left (or back.)

cloned :: Vector v a => Iso' (v a) (New v a)

Convert a `Vector` back and forth to an initializer that when run produces a copy of the `Vector`.

# Lenses

sliced

Arguments

:: Vector v a |
=> Int | `i` starting index
-> Int | `n` length
-> Lens' (v a) (v a) |

`sliced i n` provides a `Lens` that edits the `n` elements starting at index `i` from a `Lens`.

This is only a valid `Lens` if you do not change the length of the resulting `Vector`.

Attempting to return a longer or shorter vector will result in violations of the `Lens` laws.

    >>> Vector.fromList [1..10] ^. sliced 2 5
    fromList [3,4,5,6,7]

    >>> Vector.fromList [1..10] & sliced 2 5 . mapped .~ 0
    fromList [1,2,0,0,0,0,0,8,9,10]

# Traversal of individual indices

ordinals :: Vector v a => [Int] -> IndexedTraversal' Int (v a) a

This `Traversal` will ignore any duplicates in the supplied list of indices.

    >>> toListOf (ordinals [1,3,2,5,9,10]) $ Vector.fromList [2,4..40]
    [4,8,6,12,20,22]