Quiver is a library that builds upon Arrow to make functional programming in Kotlin even more accessible & delightful.

Main features include:

• Outcome type for modelling the presence, absence or error state of a value.
• Extension methods on Option, List, Validated and Either for improved error handling, combinators and interoperability with other Arrow and Kotlin types.
• Extension methods on suspended functions to allow for seamless retries of operations.

There are two published libraries.

• lib contains types and functions to provide additional functional programming idioms over and above what is available from Arrow.
• lib-test contains kotest Matchers and Arbs for writing tests that use types found in lib.

Getting Started

On the Sonatype page for Quiver, choose the latest version of lib (and lib-test if desired) and follow the instructions for inclusion in your build tool.

Quiver is a Kotlin Multiplatform library. Gradle resolves the right artifact for each target from app.cash.quiver:lib; JVM, JS, iOS, macOS, tvOS, watchOS, Linux (x64) and Windows (mingw x64) are supported. Other build tools should depend on the platform artifact directly, for example app.cash.quiver:lib-jvm.

Quiver requires Kotlin 2.2 or newer. lib-test requires Kotest 6.2.6 or newer.

Building

Install Hermit, see instructions at https://cashapp.github.io/hermit/

Use gradle to run all Kotlin tests locally:

gradle build

Documentation

The API documentation is published at https://block.github.io/quiver/. It is rebuilt from main on every merge, so it may include changes that have not been released yet.

Changelog

See a list of changes in each release in the CHANGELOG.

Contributing

For details on contributing, see the CONTRIBUTING guide.