Functional companion to Kotlin's Standard Library
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README.md

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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.

Curated external links

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.

allprojects {
    repositories {
        jcenter()
    }
}

Dependency breakdown starting in Arrow 0.9.0

Starting in 0.9.0, 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

Add the dependencies into the project's build.gradle

def arrow_version = "0.8.2"
dependencies {
    compile "io.arrow-kt:arrow-core-data:$arrow_version"
    compile "io.arrow-kt:arrow-syntax:$arrow_version"
    compile "io.arrow-kt:arrow-typeclasses:$arrow_version"
    compile "io.arrow-kt:arrow-extras:$arrow_version"
    compile "io.arrow-kt:arrow-core-extensions:$arrow_version"
    compile "io.arrow-kt:arrow-extras-extensions:$arrow_version"
    kapt    "io.arrow-kt:arrow-meta:$arrow_version"
    
    compile "io.arrow-kt:arrow-query-language:$arrow_version" //optional
    compile "io.arrow-kt:arrow-free:$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:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-extensions:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-rx2:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-rx2-extensions:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-reactor:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-reactor-extensions:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-kotlinx-coroutines:$arrow_version" //optional
    compile "io.arrow-kt:arrow-effects-kotlinx-coroutines-extensions:$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:$arrow_version" //optional
    compile "io.arrow-kt:arrow-extensions-recursion:$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

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

def arrow_version = "0.8.2"
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.