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Pipes v4.0.0

pipes is a clean and powerful stream processing library that lets you build and connect reusable streaming components.

Quick start

Then fire up ghci:

$ ghci
Prelude> import Pipes
Prelude Pipes> import qualified Pipes.Prelude as P

... and echo standard input to standard output until you enter quit.

Prelude Pipes P> runEffect $ P.stdinLn >-> P.takeWhile (/= "quit") >-> P.stdoutLn
Test[Enter]
Test
Apple[Enter]
Apple
quit[Enter]
Prelude P> -- Done!

To learn more, read the pipes tutorial.

Features

  • Concise API: Use simple commands like for, (>->), await, and yield

  • Blazing fast: Implementation tuned for speed

  • Lightweight Dependency: pipes is small and compiles very rapidly, including dependencies

  • Elegant semantics: Use practical category theory

  • ListT: Correct implementation of ListT that interconverts with pipes

  • Bidirectionality: Implement duplex channels

  • Extensive Documentation: Second to none!

Philosophy

The pipes library emphasizes the following three design precepts:

  • Emphasize elegance - Elegant libraries replace inelegant libraries

  • Theory everywhere - Principled design promotes intuitive behavior

  • Minimize dependencies - Small dependency profiles maximize portability

Outline

The core pipes ecosystem consists of the following four libraries:

  • pipes: The elegant, theoretically-principled core.

  • pipes-concurrency: Message passing and reactive programming

  • pipes-parse: Utilities for parsing streams

  • pipes-safe: Resource management and exception safety

These represent the core areas that I envision for pipes. The latter three libraries represent the more pragmatic face of the ecosystem and make design tradeoffs where there is no known elegant solution.

Derived libraries that build on top of these include:

  • pipes-network and pipes-network-tls: Networking support

  • pipes-attoparsec: High-efficiency streaming parsing

  • pipes-zlib: Compression and decompression

  • pipes-binary: Streaming serialization and deserialization

  • pipes-aeson: Streaming JSON encoding and decoding

Development Status

Build Status

The pipes ecosystem is in the middle of a transition to use the new 4.0.0 API. This version should be the last significant API change for the core pipes library, although downstream libraries may still exhibit some API instability for a couple of months as they experiment with a few new features enabled by the 4.0.0 API.

All development work currently focuses on transitioning downstream libraries to use pipes-4.0.0 and building out the pipes ecosystem.

The long term goal is to get pipes into the Haskell platform and become the basic building block for streaming APIs.

Community Resources

How to contribute

  • Contribute code

  • Build derived libraries

  • Write pipes tutorials

License (BSD 3-clause)

Copyright (c) 2012, 2013 Gabriel Gonzalez All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

  • Neither the name of Gabriel Gonzalez nor the names of other contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.