Functional Groovy is a library for doing functional programming (FP) in Groovy. It is a Groovy extension module for Functional Java (FJ), adding Groovy idioms and new FP constructs in Groovy.

Features includes:

• FunctionalJava based
• Enhances FunctionalJava for Groovy as a Groovy extension module
• Groovy Quickcheck style property testing (specification based testing)
• Monad library using a minimal monad implementation (unit/flatMap)
• Monadic functions added to the standard Java List
• Monad comprehensions (dynamically typed)
• Lenses
• Reader, Writer and State monads
• A simple IO type
• Y Combinator

The project has some cloud build servers I used to experiment with including:

• Cloudbees Jenkins Build
• Sonatype Functional Groovy Artifacts
• Travis CI Build

I have written an initial blog post on Groovy Null Handling using Bind, Comprehensions and Lift covering:

• some introductory material on functional programming in Groovy
• how to begin using the Functional Groovy library
• handling nulls by binding through the Option type, monadic comprehensions and monadic lifting

The full list of related posts are:

• Groovy Null Handling Using Bind, Comprehensions and Lift
• Specification Based Testing
• Referentially Transparent Input/Output in Groovy
• Folds and Unfolds

To start using the library add the dependency com.github.mperry:functionalgroovy-main:0.5.1-SNAPSHOT to your Gradle project. A simple test script to get going (test.groovy) is:

@GrabResolver('https://oss.sonatype.org/content/groups/public')
@Grab('com.github.mperry:functionalgroovy-core:0.5.1-SNAPSHOT')
@Grab('org.functionaljava:functionaljava:4.1')

import com.github.mperry.fg.*

1.to(5).each {
    println it
}

Run this script using groovy test.groovy.

This project uses:

• JDK 8
• Gradle 1.11
• Groovy 2.3.2
• Functional Java 4.1
• Intellij Community Edition 13.1

I have added a list of open issues so feel free to contribute. Some ways of contributing are:

• adding new functionality
• adding tests
• adding FP in Groovy examples
• adding FunctionalGroovy usage examples

Functional Groovy is divided into four components: core, main, demo, java8 and consume.

• Core enhances Functional Java with Groovy idioms
• Main adds new functionality
• Demo includes examples of FP in Groovy and usage of this library
• Java8 includes enhancements related to Java 8 types (e.g. Optional).
• Consume shows how to include FunctionalGroovy in your project