NOTE: The docs are currently at around 60% completion. They’re the present priority project, and you can track the progress on the github issue #311.

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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.

  • 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

Basic Setup

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

In your project’s root build.gradle append the jcenter repository to your list of repositories.

allprojects {
    repositories {
        jcenter()
    }
}

Add the dependencies into the project’s build.gradle

def arrow_version = "0.7.3"
dependencies {
    compile "io.arrow-kt:arrow-core:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    compile "io.arrow-kt:arrow-typeclasses:$arrow_version" 
    compile "io.arrow-kt:arrow-data:$arrow_version" 
    compile "io.arrow-kt:arrow-instances-core:$arrow_version"
    compile "io.arrow-kt:arrow-instances-data:$arrow_version"
    kapt    "io.arrow-kt:arrow-annotations-processor:$arrow_version" 

    compile "io.arrow-kt:arrow-free:$arrow_version" //optional
    compile "io.arrow-kt:arrow-mtl:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-rx2:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-reactor:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-kotlinx-coroutines:$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:$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

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

def arrow_version = "0.7.3"
dependencies {
    ...
    kapt    'io.arrow-kt:arrow-annotations-processor:$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')
    }
}