fastsum: A fast open-union type suitable for 100+ contained alternatives

This is a package candidate release! Here you can preview how this package release will appear once published to the main package index (which can be accomplished via the 'maintain' link below). Please note that once a package has been published to the main package index it cannot be undone! Please consult the package uploading documentation for more information.

[maintain]

This package provides Data.Sum, an open-union type, similar to the Union type that powers the implementation of Oleg Kiselyov's extensible-effects library.

Unlike most open-union implementations, this type is very fast to compile, even when the type-level list of alternatives contains hundreds of entries. Membership queries are constant-time, compiling to a single type-level natural lookup in a closed type family, unlike the traditional encoding of Union, which relies on recursive typeclass lookups. As such, this type lends itself to representing abstract syntax trees or other rich data structures.

This project is safe to use in production. Any performance problems at compile-time or runtime should be filed as bugs.


[Skip to ReadMe]

Properties

Versions0.1.0.0, 0.1.1.0, 0.1.1.0
Change logChangeLog.md
Dependenciesbase (>=4.7 && <5), deepseq (>=1.4 && <2), fastsum, ghc-prim (>=0.5 && <1), hashable (>=1.2 && <2), template-haskell (>=2.12 && <3) [details]
LicenseBSD-3-Clause
CopyrightRob Rix, Josh Vera, Allele Dev, Patrick Thomson 2016-2018
AuthorRob Rix, Josh Vera, Allele Dev, Patrick Thomson
Maintainerpatrickt@github.com
CategoryData
Home pagehttps://github.com/patrickt/fastsum#readme
Source repositoryhead: git clone https://github.com/patrickt/fastsum
Executablesexample
UploadedMon May 13 18:12:13 UTC 2019 by patrick_thomson

Modules

[Index]

Flags

NameDescriptionDefaultType
build-examplesDisabledAutomatic

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

Maintainers' corner

For package maintainers and hackage trustees


Readme for fastsum-0.1.1.0

[back to package description]

fastsum

This package provides Data.Sum, an open-union type, similar to the Union type that powers the implementation of Oleg Kiselyov's extensible-effects library.

Unlike most open-union implementations, this type is very fast to compile, even when the type-level list of alternatives contains hundreds of entries. Membership queries are constant-time, compiling to a single type-level natural lookup in a closed type family, unlike the traditional encoding of Union, which relies on recursive typeclass lookups. As such, this type lends itself to representing abstract syntax trees or other rich data structures.

GHC 8's support for custom type errors provides readable type errors should membership constraints not be satisfied.

In order to achieve speed, this package makes fewer guarantees about what can be proven given a Member instance. If you require a richer vocabulary to describe the implications of membership, you should use the traditional implementation of open-unions.

Credits

This library is built on the work of Oleg Kiselyov, which was then modified by Allele Dev. It was extracted from Josh Vera's effects library. Rob Rix implemented the ElemIndex type family and the Apply typeclass.