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Linear base

Linear base is a standard library for developing applications with linear types. It is named linear-base to be an analog to the original base package that ships with GHC.

The purpose of linear-base is to provide the minimal facilities you need to write practical Linear Haskell code, i.e., Haskell code that uses the -XLinearTypes language extension.

Motivation

Why do you need linear-base to write linear projects?

1. Data types, functions and classes in base are not linear types aware. For instance, if n is a linearly-bound Int, the RHS of a definition cannot write n + 1 — this will not type check. We need linear variants of Num, Functors, Monads, ($), etc.

2. This library exports new abstractions that leverage linear types for resource safety or performance. For example, there are new APIs for file and socket I/O as well as for safe in-place mutation of arrays.

Getting started

-XLinearTypes is released with GHC 9, and linear-base is released on Hackage and Stackage.

All source files with linear types need a language extension pragma at the top:

{-# LANGUAGE LinearTypes #-}

User Guide

If you already know what -XLinearTypes does and what the linear arrow a %1-> b means, then read the User Guide and explore the examples/ folder to know how to use linear-base.

You can also find a table comparing base and linear-base typeclasses here.

Learning about -XLinearTypes

If you're a Haskeller who hasn't written any Linear Haskell code, don't fear! There are plenty of excellent resources and examples to help you.

Tutorials and examples

• See the examples/ folder.
• Linear examples on watertight 3D models

Reading material

• There is a wiki page.
• Key Blog posts
  • Predictable performance (the first blog post from Tweag on this)
  • IO State Transitions
  • Streaming
  • See here for all of Tweag's blog posts on linear types.
• Here is the paper behind -XLinearTypes.

Talks

–

• Distributed Programming with Linear Types – Haskell Exchange 2017
• Practical Linearity in a higher-order polymorphic language – POPL 2018
• Practical Linearity in a higher-order polymorphic language – Curry on 2018
• Practical Linearity in a higher-order polymorphic language – Haskell Exchange 2018
• Implementing Linear Haskell
• In-place array update with linear types – ZuriHac 2020
• Typecheck Your Memory Management with Linear Types – Haskell Exchange 2017

Contributing

Linear base is maintained by Tweag.

To contribute please see the Design Document for instructions and advice on making pull requests.

Licence

See the Licence file.

Copyright © Tweag Holding and its affiliates.