[](https://maven-badges.herokuapp.com/maven-central/io.arrow-kt/arrow-core) [](https://travis-ci.org/arrow-kt/arrow/) [](https://kotlinlang.org/docs/reference/whatsnew13.html) [](http://www.apache.org/licenses/LICENSE-2.0) [](https://codecov.io/gh/arrow-kt/arrow) Λrrow is a library for Typed Functional Programming in Kotlin. Arrow aims to provide a [*lingua franca*](https://en.wikipedia.org/wiki/Lingua_franca) of interfaces and abstractions across Kotlin libraries. For this, it includes the most popular data types, type classes and abstractions such as `Option`, `Try`, `Either`, `IO`, `Functor`, `Applicative`, `Monad` to empower users to write pure FP apps and libraries built atop higher order abstractions. Use the list below to learn more about Λrrow's main features. - [Documentation](http://arrow-kt.io) - [Patterns](http://arrow-kt.io/docs/patterns/glossary/): tutorials and approaches to day-to-day challenges using FP - [Libraries](http://arrow-kt.io/docs/quickstart/libraries/): all the libraries provided by Λrrow - [Type classes](http://arrow-kt.io/docs/typeclasses/intro/): defining behaviors for data - [Data types](http://arrow-kt.io/docs/datatypes/intro/): common abstractions - [Effects](http://arrow-kt.io/docs/effects/io/): interfacing with external systems - [Optics](http://arrow-kt.io/docs/optics/iso/): inspecting and modifying data structures #### Curated external links - [Projects and Examples](http://arrow-kt.io/docs/quickstart/projects/) - [Blogs and Presentations](http://arrow-kt.io/docs/quickstart/blogs/) #### Join Us Arrow is an inclusive community powered by awesome individuals like you. As an actively growing ecosystem, Arrow and its associated libraries and toolsets are in need of new contributors! We have issues suited for all levels, from entry to advanced, and our maintainers are happy to provide 1:1 mentoring. All are welcome in Arrow. If you’re looking to contribute, have questions, or want to keep up-to-date about what’s happening, please follow us here and say hello! - [Arrow on Twitter](https://twitter.com/arrow_kt) - [#Arrow on Kotlin Slack](https://kotlinlang.slack.com/) - [Arrow on Gitter](https://gitter.im/arrow-kt/Lobby) # Basic Setup Make sure to have the latest version of JDK 1.8 installed. Add it in your root `build.gradle` at the end of repositories. ```groovy allprojects { repositories { jcenter() } } ``` # Dependency breakdown starting in Arrow 0.9.1 Starting in 0.9.1, Arrow follows the following convention for artifact publication. The arrow modules are Core, Effects, Optics, Recursion, etc. An Arrow module is composed of data types and type classes. Arrow modules are exported and published with the following semantics. If we take for example `arrow-core`. Arrow core contains the basic arrow type classes and data types and it's composed of 3 main artifacts that may be used a la carte: Recomended for most use cases: - `arrow-core` (Depends on data and extensions modules and exports both) Trimmed down versions: - `arrow-core-data` (Only data types) - `arrow-core-extensions` (Only type class extensions) # Current stable version 0.9.0 ```groovy def arrow_version = "0.9.0" dependencies { compile "io.arrow-kt:arrow-core-data:$arrow_version" compile "io.arrow-kt:arrow-core-extensions:$arrow_version" compile "io.arrow-kt:arrow-syntax:$arrow_version" compile "io.arrow-kt:arrow-typeclasses:$arrow_version" compile "io.arrow-kt:arrow-extras-data:$arrow_version" compile "io.arrow-kt:arrow-extras-extensions:$arrow_version" kapt "io.arrow-kt:arrow-meta:$arrow_version" compile "io.arrow-kt:arrow-query-language:$arrow_version" //optional compile "io.arrow-kt:arrow-free-data:$arrow_version" //optional compile "io.arrow-kt:arrow-free-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-mtl:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-data:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-io-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-rx2-data:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-rx2-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-reactor-data:$arrow_version" //optional compile "io.arrow-kt:arrow-effects-reactor-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-optics:$arrow_version" //optional compile "io.arrow-kt:arrow-generic:$arrow_version" //optional compile "io.arrow-kt:arrow-recursion-data:$arrow_version" //optional compile "io.arrow-kt:arrow-recursion-extensions:$arrow_version" //optional compile "io.arrow-kt:arrow-query-language:$arrow_version" //optional compile "io.arrow-kt:arrow-integration-retrofit-adapter:$arrow_version" //optional } ``` # Additional Setup For projects that wish to use their own `@higherkind`, `@optics` and other meta programming facilities provided by Λrrow the setup below is also required: Add the dependencies into the project's `build.gradle` ```groovy apply plugin: 'kotlin-kapt' //optional apply from: rootProject.file('gradle/generated-kotlin-sources.gradle') //only for Android projects def arrow_version = "0.9.0" dependencies { ... kapt 'io.arrow-kt:arrow-meta:$arrow_version' //optional ... } ``` `gradle/generated-kotlin-sources.gradle` ```groovy apply plugin: 'idea' idea { module { sourceDirs += files( 'build/generated/source/kapt/main', 'build/generated/source/kapt/debug', 'build/generated/source/kapt/release', 'build/generated/source/kaptKotlin/main', 'build/generated/source/kaptKotlin/debug', 'build/generated/source/kaptKotlin/release', 'build/tmp/kapt/main/kotlinGenerated') generatedSourceDirs += files( 'build/generated/source/kapt/main', 'build/generated/source/kapt/debug', 'build/generated/source/kapt/release', 'build/generated/source/kaptKotlin/main', 'build/generated/source/kaptKotlin/debug', 'build/generated/source/kaptKotlin/release', 'build/tmp/kapt/main/kotlinGenerated') } } ``` # License Copyright (C) 2017 The Λrrow Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.