vector-rotcev: Vectors with O(1) reverse
A wrapper for an arbitrary Vector with O(1) reverse.
Instead of creating a copy, it just flips a flag, which inverts indexing.
Imagine it as a vector with a switch between little-endianness and big-endianness.
[Skip to Readme]
Downloads
- vector-rotcev-0.1.0.1.tar.gz [browse] (Cabal source package)
- Package description (revised from the package)
Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.
Maintainer's Corner
For package maintainers and hackage trustees
Candidates
- No Candidates
| Versions [RSS] | 0.1.0.0, 0.1.0.1, 0.1.0.2 |
|---|---|
| Change log | changelog.md |
| Dependencies | base (>=4.9 && <5), vector (<0.13) [details] |
| License | BSD-3-Clause |
| Copyright | 2019-2021 Andrew Lelechenko |
| Author | Andrew Lelechenko |
| Maintainer | Andrew Lelechenko <andrew.lelechenko@gmail.com> |
| Revised | Revision 1 made by Bodigrim at 2023-01-14T18:59:52Z |
| Category | Data, Data Structures |
| Home page | https://github.com/Bodigrim/rotcev |
| Source repo | head: git clone https://github.com/Bodigrim/rotcev |
| Uploaded | by Bodigrim at 2021-09-06T21:51:56Z |
| Distributions | LTSHaskell:0.1.0.2, NixOS:0.1.0.2, Stackage:0.1.0.2 |
| Downloads | 969 total (19 in the last 30 days) |
| Rating | (no votes yet) [estimated by Bayesian average] |
| Your Rating | |
| Status | Docs available [build log] Last success reported on 2021-09-06 [all 1 reports] |
Readme for vector-rotcev-0.1.0.1
[back to package description]vector-rotcev 
A wrapper for an arbitrary Vector with O(1) reverse. Instead of creating a copy, it just flips a flag, which inverts indexing. Imagine it as a vector with a switch between little-endianness and big-endianness.
Let us have a vector of data vec :: Vector Int, which is manipulated via Data.Vector.Generic-based API. You can wrap it into Forward vec :: Rotcev Vector Int and leave everything else unchanged, because Rotcev Vector Int still has all Vector instances. Then apply reverse (Forward vec) :: Rotcev Vector Int, which effectively reverses the vector in O(1) time and space. Internally instead of actual reversing, reverse just provides a view (or a lens) with an inverted order of indexing, which affects all Data.Vector.Generic API.
For example,
> vec = Data.Vector.Generic.fromList [0..100] :: Data.Vector.Vector Int
> cev = reverse (Forward vec) :: Rotcev Data.Vector.Vector Int
> cev Data.Vector.Generic.! 10
90
In a mutable setting you can freely manipulate original and reversed vectors simultaneously, using mreverse function:
> Control.Monad.ST.runST $ do
vec <- Data.Vector.Generic.Mutable.replicate 3 0.0
let cev = mreverse vec
Data.Vector.Generic.Mutable.write vec 0 1.0
Data.Vector.Generic.Mutable.write cev 0 2.0
unRotcev <$> Data.Vector.Generic.freeze vec
:: Data.Vector.Vector Double
[1.0,0.0,2.0]
This library works for any flavor of Vector: boxed, unboxed, storable, whatever.