Arrow aims to bring idiomatic functional programming to Kotlin. This means Arrow is inspired by the great work made in other functional programming communities, yet exposes these ideas and concepts in ways that do not feel alien to Kotlin programmers.

Arrow comprises different libraries, each improving or extending one commonly-used library in the Kotlin ecosystem or a particular Kotlin language feature.

In a rush?

Our summary is designed to help you find your way in the Arrow ecosystem.

Quickstart

Gradle or Maven, JVM or Multiplatform, Arrow fits in all your projects

Typed errors

Learn how to work with typed errors

Coroutines

Concurrency and parallelism

Resilience

Act in an organized way when failures occur

Immutable data

Concise ways to handle immutable data

Collections and functions

Utilities for more productive basics

Design

Recipes for designing nice Kotlin code

Integrations

Playing nice with the rest of the ecosystem

Each section in the documentation roughly corresponds to one of the libraries that compose Arrow.

• In our Quickstart, you can read how to introduce Arrow in your project.
• No library lives in a vacuum, and Arrow enjoys integrations with many other popular Kotlin libraries.
• We also provide guidance on broader design and architecture using functional programming concepts.

Library	Features
arrow-core Companion to Kotlin's standard library	Typed errors, including Raise, Either, and Option Non-empty collections Memoized recursive functions
arrow-fx-coroutines Companion to KotlinX Coroutines	High-level concurrency, including parMap and parZip Resource management (with suspend)
arrow-autoclose	Resource management (no suspend)
arrow-resilience	Resilience patterns
arrow-optics + arrow-optics-ksp-plugin Companion to data and sealed classes	Utilities for immutable data
arrow-fx-stm	Software Transactional Memory (STM)
arrow-atomic Multiplatform-ready references	Atomic references
arrow-collectors Companion to fold and reduce	Aggregation with single traversal
arrow-eval More powerful laziness	Control over evaluation
arrow-functions Part of arrow-core in 1.x	Utilities for functions
arrow-core-high-arity	arrow-core for more than 10 parameters

Library	Integrates with
arrow-core-serialization	KotlinX Serialization for core types
arrow-cache4k	cache4k for memoization
arrow-optics-compose	Compose state management with optics

We'd love to hear from you!

We're always looking for ways to improve the libraries and the documentation. Feel free to open an issue in our repository with any suggestions or feedback. Thanks in advance! 🤩