På samma sätt som alla C#-programmerare idag vet att de egentligen för länge sedan borde ha gått över till F# vet Java-programmerare att de borde gått över till Scala eller ännu hellre OCaml-Java eller liknande.

Tyvärr finns fortfarande programmerare som - av olika skäl - ännu inte haft möjligheten att helt och fullt byta upp sig. Dessa stackare söker givetvis efter stöd av olika former och vi som följer frågeställningarna som dyker upp på t.ex. stackoverflow.com vet att frågan om FP-bibliotek för dessa språk är återkommande.

För de stackars C#-programmerarna finns idag följande hjälp att tillgå:

• FpSharp - This library provides functional programming abstrations for .NET and C# including map, fold, filter functions for ordinary .NET collections, the option data type, a lazy type, a functional list type, lazy functional lists, and more.
• Functional C# - This is a set of libraries to demonstrate functional programming aspects as implemented in C#. This is not to imply that C# is a functional language, but can implement some of the aspects of it. This project is to demonstrate some of those techniques
• Elevate - Elevate is an easy to pick up library containing things you wish were in the BCL. Use one component or many. Contribute your own utilities. Help us make Boost for .NET.
  Elevate is developed in C#. Currently, we're focused on adding concepts from functional languages.
• Kinet - Kinet is a library for C# that provides useful data structures and algorithms for general purpose programming. It is somewhat inspired by the Functional Java project and the Haskell programming language.
• Functional .Net - C# 3.0 and VB 9 provide strong elements of functional programming in mainstream languages (lambda expressions, extension methods, a weak version of type inference for local variables, etc.)
  The library support for them, however, is pretty much limited to IEnumerable<T> and LINQ. This project is intended to extend it by providing additional data structures, algorithms, and extension methods.
• Sasa - Sasa is a collection of useful C# extensions to the standard library. There are tuples, Linq extensions, full MIME e-mail parsing, a POP3 client, array combinators, compact serialization, purely functional lists, lazy types, and more.

Luca Bolognese har också (utan att mig veterligen paketera sin kod) skrivit en läsvärd artikelserien i ämnet: "A C# library to write functional code"(Background, Tuples, Records, Type Unions och The Match operator).

På Java-sidan finns också vissa möjligheter:

• Functional Java - Functional Java is an open source library that aims to prepare the Java programming language for the inclusion of closures. It also serves as a platform for learning functional programming concepts [...]
• FunctionalJ - FunctionalJ is a library which makes it easy to use functional programming constructs in Java code.
• Jambda - Jambda is an attempt to provide the Java(TM) world with tools and concepts from functional programming (FP). (Här har jag själv haft viss inblanding)
• LambdaJ - Manipulate collections in a pseudo-functional and statically typed way.