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Functional Groovy

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:

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:

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:


import com.github.mperry.fg.* {
    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


Functional programming in Groovy



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