Open Source Haskell Libraries

Documentation can be found on Hackage. Changes between versions are recorded in the change log. When building this package directly from the Git repository, one must run autoreconf -fi to generate the configure script needed by cabal configure. This requires Autoconf to be installed.

Polysemy is a high-performance, zero-boilerplate effect system for Haskell, designed to simplify the handling of side effects in functional programs. Unlike traditional monad transformer stacks, Polysemy uses a modern approach based on freer monads and interpreters, allowing developers to define, compose, and interpret effects in a more modular and testable way. It aims to offer both flexibility and performance without sacrificing type safety or expressiveness.

Assorted projects. General-purpose libraries for Python, C++, Scala, bash, and others. Meta-programming tools. System utilities. UI components. Web APIs. Configuration files. Benchmarks. Programming competition entries. And much more.

Beam is a Haskell interface to relational databases. Beam uses the Haskell type system to verify that queries are type-safe before sending them to the database server. Queries are written in a straightforward, natural monadic syntax. Combinators are provided for all standard SQL92 features, and a significant subset of SQL99, SQL2003, and SQL2008 features. Beam is standards-compliant but not naive. We recognize that different database backends provide different guarantees, syntaxes, and advantages. To reflect this, Beam maintains a modular design. While the core package provides standard functionality, Beam is split up into a variety of backends which provide a means to interface Beam's data query and update DSLs with particular RDBMS backends. Backends can be written and maintained independently of this repository. For example, the beam-MySQL and beam-firebird backends are packaged independently.

Haxl is a Haskell library that simplifies access to remote data, such as databases or web-based services. Haxl can automatically batch multiple requests to the same data source, request data from multiple data sources concurrently, cache previous requests, and memoize computations. Having all this handled for you behind the scenes means that your data-fetching code can be much cleaner and clearer than it would otherwise be if it had to worry about optimizing data-fetching. To use Haxl in your own application, you will likely need to build one or more data sources: the thin layer between Haxl and the data that you want to fetch, be it a database, a web API, a cloud service, or whatever. There is a generic datasource in "Haxl.DataSource.ConcurrentIO" that can be used for performing arbitrary IO operations concurrently, given a bit of boilerplate to define the IO operations you want to perform.

Soutei is a trust-management system for access control in distributed systems. Soutei policies and credentials are written in a declarative logic-based language. Soutei policies are modular, concise, readable, supporting conditional delegation.

This library implements Haskell API client for popular Web3 platforms.

An R5RS Scheme interpreter and library written in Haskell. Provides advanced features including continuations, hygienic macros, and the full numeric tower.

relude is a safe, performant, user-friendly and lightweight Haskell standard library. The default Prelude is not perfect and doesn’t always satisfy one’s needs. At this stage, you may want to try an alternative prelude library. relude has some strong goals and principles that it sticks to. That principles define the library's decisions and might tell you more about the priorities of the library. You can be more productive with a “non-standard” standard library, and relude helps you with writing safer and more efficient code faster. Usage of partial functions can lead to unexpected bugs and runtime exceptions in pure code. The types of partial functions lie about their behaviour. And even if it is not always possible to rely only on total functions, relude strives to encourage best-practices and reduce the chances of introducing a bug.