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.
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| Versions [RSS] | 0.1.0.0, 0.1.0.1, 0.1.0.2 |
|---|---|
| Change log | changelog.md |
| Dependencies | base (>=4.9 && <5), vector [details] |
| Tested with | ghc ==9.4.4, ghc ==9.2.5, ghc ==9.0.2, ghc ==8.10.4, ghc ==8.8.4, ghc ==8.6.5, ghc ==8.4.4, ghc ==8.2.2, ghc ==8.0.2 |
| License | BSD-3-Clause |
| Copyright | 2019-2021 Andrew Lelechenko |
| Author | Andrew Lelechenko |
| Maintainer | Andrew Lelechenko <andrew.lelechenko@gmail.com> |
| 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 2023-01-14T19:56:28Z |
| Distributions | LTSHaskell:0.1.0.2, NixOS:0.1.0.2, Stackage:0.1.0.2 |
| Downloads | 1157 total (9 in the last 30 days) |
| Rating | (no votes yet) [estimated by Bayesian average] |
| Your Rating | |
| Status | Docs available [build log] Last success reported on 2023-01-14 [all 1 reports] |
Readme for vector-rotcev-0.1.0.2
[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.