first-class-patterns: First class patterns and pattern matching, using type families

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This package implements a library of first class patterns. The initial basis for this library was Morten Rhiger's "Type-safe pattern combinators"; the patterns can be used in an almost identical way to those of Morten Rhiger. In a series of blog posts at the types of patterns were made more revealing using type families, and a simpler implementation was used which avoids some book-keeping.

The library reimplements most of Haskell's built-in pattern matching facilities, plus some more. The pattern matches of this library are lightweight: when GHC's optimisation is turned on, all overhead should be optimised away, leaving a standard Haskell pattern match.

If you're just reading the documentation for this library for the first time, start with Data.Pattern.

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Versions 0.1.0, 0.2.0, 0.3.0, 0.3.1, 0.3.2,,,,,,
Change log
Dependencies base (>= && <5), transformers (>=0.1.0 && <0.6) [details]
License BSD-3-Clause
Author Reiner Pope, Brent Yorgey
Maintainer Kowainik <>
Category Data, Pattern
Home page
Bug tracker
Source repo head: git clone git://
Uploaded by shersh at 2019-10-01T18:22:10Z


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Implements patterns in Haskell as first class objects.