cluss: simple alternative to type classes

[ bsd3, constraints, library, type-system ] [ Propose Tags ]

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 In with a list of "type patterns" like 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".

Cluss instances are closed and cluss methods are open, unlike type classes, whose instances are open and whose methods are closed.

Clusses can easily be used in a nested way, and can even be recursive, just like recursive type classes, and therefore clusses are expressive enough to imitate Haskell-98-style type classes.

More information can be found in the Haddock or the comments in the source code. The updated haddock is here:




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Versions [RSS] 0.1, 0.2, 0.3
Dependencies base (>=4 && <5) [details]
License BSD-3-Clause
Copyright Copyright (C) 2014 Yusuke Matsushita
Author Yusuke Matsushita
Maintainer Yusuke Matsushita <>
Revised Revision 4 made by Kinokkory at 2014-10-05T12:05:45Z
Category type system, constraints
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Uploaded by Kinokkory at 2014-10-03T14:01:20Z
Reverse Dependencies 2 direct, 0 indirect [details]
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