Λrrow is a library for Typed Functional Programming in Kotlin.

Arrow aims to provide a 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
• Patterns: tutorials and approaches to day-to-day challenges using FP
• Libraries: all the libraries provided by Λrrow
• Type classes: defining behaviors for data
• Data types: common abstractions
• Effects: interfacing with external systems
• Optics: inspecting and modifying data structures

Curated external links

• Projects and Examples
• Blogs and Presentations

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
• #Arrow on Kotlin Slack
• Arrow on Gitter

Basic Setup

Make sure to have the latest version of JDK 1.8 installed.

Add this in your root build.gradle at the end of repositories.

allprojects {
    repositories {
        mavenCentral()
        jcenter()
        maven { url "https://dl.bintray.com/arrow-kt/arrow-kt/" } 
        maven { url 'https://oss.jfrog.org/artifactory/oss-snapshot-local/' } // for SNAPSHOT builds
    }
}

Next development version 0.10.0

Add the dependencies into the project's build.gradle

Λrrow Core

def arrow_version = "0.10.0-SNAPSHOT"
dependencies {
    compile "io.arrow-kt:arrow-core:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    kapt    "io.arrow-kt:arrow-meta:$arrow_version"
}

Λrrow Core + Λrrow Optics

def arrow_version = "0.10.0-SNAPSHOT"
dependencies {
    compile "io.arrow-kt:arrow-optics:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    kapt    "io.arrow-kt:arrow-meta:$arrow_version"
}

Λrrow Core + Λrrow Fx

def arrow_version = "0.10.0-SNAPSHOT"
dependencies {
    compile "io.arrow-kt:arrow-fx:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    kapt    "io.arrow-kt:arrow-meta:$arrow_version"
}

Λrrow Core + Λrrow Optics + Λrrow Fx

def arrow_version = "0.10.0-SNAPSHOT"
dependencies {
    compile "io.arrow-kt:arrow-fx:$arrow_version"
    compile "io.arrow-kt:arrow-optics:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    kapt    "io.arrow-kt:arrow-meta:$arrow_version"
}

Here is the complete library list for a more granular dependency set-up.

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

apply plugin: 'kotlin-kapt' //optional
apply from: rootProject.file('gradle/generated-kotlin-sources.gradle') //only for Android projects

def arrow_version = "0.10.0-SNAPSHOT"
dependencies {
    ...
    kapt    'io.arrow-kt:arrow-meta:$arrow_version' //optional
    ...
}

gradle/generated-kotlin-sources.gradle

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.