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Compositional pipelines

Latest on Hackage:0.1.0

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow to host generated Haddocks.

BSD3 licensed by Gabriel Gonzalez, Paolo Capriotti
Maintained by

This library offers an abstraction similar in scope to iteratees/enumerators/enumeratees, but with different characteristics and naming conventions.

This package is a fork of the original pipes package by Gabriel Gonzalez. See for a comparison between the two packages.

Differences with traditional iteratees:

  • Simpler semantics: There is only one data type (Pipe), two basic primitives (await and yield), and only one way to compose Pipes (>+>). In fact, (>+>) is just convenient syntax for the composition operator in Category. Most pipes can be implemented just using the Monad instance and composition.

  • Different naming conventions: Enumeratees are called Pipes, Enumerators are Producers, and Iteratees are Consumers. Producers and Consumers are just type synonyms for Pipes with either the input or output end closed.

  • Pipes form a Category: that means that composition is associative, and that there is an identity Pipe.

  • Vertical concatenation works on every Pipe: (>>), concatenates Pipes. Since everything is a Pipe, you can use it to concatenate Producers, Consumers, and even intermediate Pipe stages. Vertical concatenation can be combined with composition to create elaborate combinators, without the need of executing pipes in "passes" or resuming partially executed pipes.

Check out Control.Pipe for a copious introduction (in the spirit of the iterIO library), and Control.Pipe.Combinators for some basic combinators and Pipe examples.

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