Bluefin

Bluefin is an effect system for Haskell which allows you, through value-level capabilities, to freely mix a variety of effects including

• Bluefin.EarlyReturn, for early return
• Bluefin.Exception, for exceptions
• Bluefin.IO, for I/O
• Bluefin.State, for mutable state
• Bluefin.Stream, for streams

Introduction

For an introduction to Bluefin, see the docs in the Bluefin module.

Examples

There is an bluefin-examples package which you can see in this repository at bluefin-examples/src/Bluefin/Examples.

Poor performance under GHC 9.12.1 and 9.12.2

Due to a bug in GHC 9.12.1 and 9.12.2, Bluefin performance suffers greatly on those compilers. The bug will be fixed in GHC 9.12.3 and 9.14.1. See https://github.com/tomjaguarpaw/bluefin/issues/77 for more details.

Contact

If you have a question about Bluefin, you think you might have found a bug, you're stuck on something, or you want to make contact for any other reason then either open an issue or start a discussion, whichever you prefer.

Contributing

If you would like to add a new function to Bluefin, please prefer to add it to the bluefin-contrib package, where all user contributions will be accepted by default. If you think a function in bluefin-contrib deserves to be exported from bluefin itself, please open an issue.

Acknowledgements

Tom Ellis would like to thank many individuals for their work related to effect systems. Without the work of these individuals, Bluefin would not exist.

• Oleg Kiselyov, particularly for his work on effects and delimited continuations

• Michael Snoyman, particularly for his work on conduit and the ReaderT IO pattern

• Gabriella Gonzalez, particularly for her work on pipes

• Alexis King, particularly for her work on effect systems and delimited continuations

• David Feuer, particularly for his observation about handlers and rank-2 types

• Andrzej Rybczak for his work on effectful

• Francois Pottier for "Wandering through linear types, capabilities, and regions"

• Jasper van de Jeugt, particularly for promoting the handle pattern

• Michael Thompson, for his work on streaming

• Ningning Xie and Daan Leijen, for their work on Koka

• Andrej Bauer and Matija Pretnar, for their work on Eff

• Sjoerd Visscher, for his work on effects