https://github.com/VinylRecords/Vinyl

Extensible Records for Haskell. Pull requests welcome! Come visit us on #vinyl on freenode.
https://github.com/VinylRecords/Vinyl

Last synced: 3 months ago
JSON representation

Extensible Records for Haskell. Pull requests welcome! Come visit us on #vinyl on freenode.

• Host: GitHub
• URL: https://github.com/VinylRecords/Vinyl
• Owner: VinylRecords
• License: mit
• Created: 2012-10-26T03:36:57.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2023-10-28T07:29:29.000Z (over 1 year ago)
• Last Synced: 2024-08-02T01:26:43.273Z (6 months ago)
• Language: Haskell
• Homepage: http://hackage.haskell.org/package/vinyl
• Size: 840 KB
• Stars: 260
• Watchers: 14
• Forks: 49
• Open Issues: 43
• Metadata Files:
  • Readme: README.markdown
  • Changelog: CHANGELOG.md
  • License: LICENSE

Awesome Lists containing this project

README

        
Vinyl is a general solution to the records problem in Haskell using type level strings and other modern GHC features, featuring static structural typing (with a subtyping relation), and automatic row-polymorphic lenses. All this is possible without Template Haskell.

First, install Vinyl from [Hackage](http://hackage.haskell.org/package/vinyl):

    cabal update

    cabal install vinyl

To learn more, [try this tutorial](https://github.com/VinylRecords/Vinyl/blob/master/tests/Intro.lhs).

## Performance Scaling

Vinyl is an approach to records in Haskell based on a heterogeneous list type: a list where each element may have a different type. Since it is a list, accessing any individual field of a Vinyl record seems as though it should have *O(n)* complexity, with *n* the size of the record. Sure enough, pattern matching on a Vinyl record works just as with a list: we peel off the head element until we reach the one we are looking for. But we have an option to change these asymptotics.

If we anticipate frequent `get` operations on a record, we can use the function `toARec :: Rec f ts -> ARec f ts` to produce an *array-backed `Rec`* that offers constant-time field access. We can consider a [benchmark](https://github.com/VinylRecords/Vinyl/blob/master/benchmarks/AccessorsBench.hs) of getting specific fields from different varieties of Vinyl records.

This benchmark suggests the trends we should expect

* Getting a field deeper in a Vinyl record takes more time than getting one earlier (i.e. it appears to the left, or under fewer `:&` constructors) in the record

* Getting a field of an `ARec` (or `AFieldRec`, which is an `ARec` with named fields) array-backed record does not depend on where in the record that field lies

The x-axis of this graph should be labeled as *nanoseconds*.

![Accessors benchmark plot](/images/accessors.png)