cluss: simple alternative to type classes
A cluss enables you to achieve function overloading, or ad-hoc polymorphism, without creating a new type class.
In order to give ad-hoc polymorphism to a type variable a
,
you simply use
with a list of "type patterns" like In
In [Type T, ...] a
,
which indicates that the type matches some of the patterns;
which is analogous to a type class indicating that a type matches some of its "instances".
The constraint In [Type T, ...] a
is what we call a "cluss".
Clusses can easily be used in a nested way and even be recursive; therefore, they are expressive enough to imitate Haskell-98-style type classes.
Clusses, however, go beyond a mere alternative to type classes. They have closed and prioritized instances and open methods, while type classes have open and unprioritized instances and closed methods. Those properties give clusses the advantages different from type classes:
You can judge whether a type
a
belongs to a cluss
, on some level, writingIn
asHas as a
, since cluss instances are closed.You can make cluss instances more flexibly, without causing overlapping instances or incoherent instances, since cluss instances are prioritized.
You can create new methods for clusses anywhere in any module, since cluss methods are open.
More information can be found in the hackage's haddock or the updated haddock.
Downloads
- cluss-0.3.tar.gz [browse] (Cabal source package)
- Package description (as included in the package)
Maintainer's Corner
For package maintainers and hackage trustees
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Versions [RSS] | 0.1, 0.2, 0.3 |
---|---|
Dependencies | base (>=4 && <5), template-haskell (>=2.5) [details] |
License | BSD-3-Clause |
Copyright | (c) Yusuke Matsushita 2014 |
Author | Yusuke Matsushita |
Maintainer | Yusuke Matsushita <y.skm24t@gmail.com> |
Category | type system, constraints |
Home page | https://github.com/Kinokkory/cluss |
Bug tracker | https://github.com/Kinokkory/cluss/issues |
Source repo | head: git clone git@github.com:Kinokkory/cluss.git |
Uploaded | by Kinokkory at 2014-10-14T08:06:01Z |
Distributions | |
Reverse Dependencies | 2 direct, 0 indirect [details] |
Downloads | 3498 total (16 in the last 30 days) |
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Status | Docs uploaded by user Build status unknown [no reports yet] |