lens-4.15.3: Lenses, Folds and Traversals

Copyright | (C) 2012-16 Edward Kmett
License | BSD-style (see the file LICENSE)
Maintainer | Edward Kmett <ekmett@gmail.com>
Stability | provisional
Portability | non-portable
Safe Haskell | Trustworthy
Language | Haskell98

Data.Vector.Lens

Contents

- Isomorphisms
- Lenses
- Traversal of individual indices

Description

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

Synopsis

- toVectorOf :: Getting (Endo [a]) s a -> s -> Vector a
- vector :: Iso [a] [b] (Vector a) (Vector b)
- forced :: Iso (Vector a) (Vector b) (Vector a) (Vector b)
- sliced :: Int -> Int -> Lens' (Vector a) (Vector a)
- ordinals :: [Int] -> IndexedTraversal' Int (Vector a) a

# Documentation

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

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

    >>> toVectorOf both (8,15) == Vector.fromList [8,15]
    True

# Isomorphisms

vector :: Iso [a] [b] (Vector a) (Vector b) #

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

    >>> [1,2,3] ^. vector == Vector.fromList [1,2,3]
    True

    >>> [1,2,3] ^. vector . from vector
    [1,2,3]

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

forced :: Iso (Vector a) (Vector b) (Vector a) (Vector b) #

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

# Lenses

sliced #

Arguments

:: Int | `i` starting index
-> Int | `n` length
-> Lens' (Vector a) (Vector 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 == Vector.fromList [3,4,5,6,7]
    True

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

# Traversal of individual indices

ordinals :: [Int] -> IndexedTraversal' Int (Vector 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]