22 BEST Functional Programming Languages In 2024

Review and compare the popular Functional Programming Languages with features, pros, and cons in this tutorial:

In this tutorial, we will learn about the top functional programming languages that software developers should learn or get familiar with in order to keep up the development pace of new languages and keep up to speed with the current trends in the market.

Functional programming has been there for around six decades, but it is quickly gaining traction now, due to current trends like parallel computing, data science, and machine learning applications, etc.

Languages like Python, Rust, Typescript offer a lot of advantages – be it easy to learn syntax, applications in concurrent and multithreaded programming as well as the availability of enormous community support with great packages and libraries available for reuse.

Functional Programming Languages – Overview

Below is a chart depicting the market share of programming languages over time:

Frequently Asked Questions

Q #1) Is Python a functional Language?

Answer: Python can be used as a fully OOP language as well as functional programming since it supports functions as first-class citizens. i.e. you can assign functions to variables, pass functions as parameters, etc.

Sample code to showcase functional program in Python:

def sum(a, b):
    return (a + b)
print(sum(3,5))
funcAssignment = sum
print(funcAssignment(3,5))

//Output

8

8

Above you can see, we have assigned the function sum() to variable funcAssignment and called the same function with the variable to which the function was assigned.

Q #2) Which language is best for functional programming?

Answer: With the availability of multiple functional programming languages like Haskell, Erlang, Elixir, etc, the options are multiple, but depending on the use case and familiarity, developers can choose a language that’s best suited to their needs.

For example, real-time messaging applications can be built using Erlang or Elixir, while Haskell is better suited for building quick prototypes and applications that require a lot of scalability and concurrency.

Q #3) What are the four types of programming languages?

Answer: There are multiple types of programming languages depending on the way they function.

The major types are:

• Procedural Programming Language: With these, the emphasis is on how the result is derived – i.e. the procedure is given importance – For example, C
• Functional Programming language: Here the primary focus is on defining the result that is expected, rather than how you get that result – For example, Haskell, Erlang.
• Object-Oriented Programming language: Application is divided into entities called objects and all the communication between objects happens through messaging. The main concept is encapsulation, which means that everything that an object needs is encapsulated within the object. For example: Java, C++, C#
• Scripting Programming Languages: These are general-purpose languages and support both OOP concepts as well as functional programming language constructs – For example, Javascript, Python.

Q #4) Is functional programming the future?

Answer: Functional programming has existed for over 6 decades but still it has not overcome the use of other OOP languages like Java, C#, etc. Functional programming is definitely gaining popularity owing to mostly huge growth in data science and machine learning and with greater support for concurrency, these languages find a good place for such applications.

So, it’s good for the community for both OOPs and FP languages to co-exist and developers can choose the language framework that best suits their needs.

There are languages like Kotlin and Python which support both Object-Oriented as well as functional programming constructs.

Q #5) Is SQL functional or Object-Oriented?

Answer: SQL doesn’t come under the category of both functional and Object-oriented. It’s rather a declarative language, which implies that you basically define what you want and the SQL engine decides how that needs to be performed.

Q #6) Is Haskell faster than Python?

Answer: Haskell is a purely functional programming language while Python is more suited as an Object Oriented Programming language.

Also, an important difference between these 2 is Haskell is a compiled language with highly optimized native code compilers while Python is interpreted. So, in terms of speed, Haskell has an edge over Python.

Q #7) What is Functional Programming?

Answer: A pure function is a set of coding statements whose output is derived solely from the input parameters that it gets with no side effects. A functional program consists of an evaluation of pure functions.

Some properties are:

• You describe the result that’s expected rather than the steps you would need to get that result.
• The function is transparent – i.e. its output depends on the input parameters supplied.
• Functions can be run in parallel – as function execution should not have any side effects for other parallel threads in execution.

List of the Best Functional Programming Language

Here is the list of functional programming languages we are going to learn in this tutorial:

1. Clojure
2. Elixir
3. Haskell
4. Scala
5. Python
6. Elm
7. F#
8. Erlang
9. PHP
10. Javascript
11. Java
12. C++
13. Idris
14. Scheme
15. Go
16. Rust
17. Kotlin
18. C#
19. TypeScript
20. ReasonML
21. PureScript
22. Swift

Comparison Chart Of Functional Programming Languages

#1) Clojure

Best for people looking for a compiled general-purpose functional programming language and something that’s fully compatible with JVM.

Clojure is a dynamic and general-purpose programming language that combines interactive development along with sound infrastructure which can handle multithreaded programming.

Features:

• Compiled language, but still supports most of the features of interpreted development.
• Easy access to Java framework.
• Clojure language borrows good design/structure from other languages like – Lisps.

Pros:

• Immutable data structure helps in multi-threaded programming.
• It runs on the JVM which is a globally accepted environment.
• Doesn’t have a lot of syntactic sugar.

Cons:

• Exceptional handling is not straightforward.
• Clojure stack traces are huge, which are difficult to debug.
• Huge learning curve.
• Lack of explicit types.
• Macros are powerful but their syntax is ugly.

Website: Clojure 

#2) Elixir

Best for automated Unit testing for developers on Visual Studio Code editor and work on JS, TypeScript, and Python-based applications.

Elixir is used to build scalable and highly maintainable apps. It makes use of Erlang VM, which can support low latency distributed and fault-tolerant applications.

Features:

• It’s a high concurrency and low latency programming language.
• It combines the best features of Erlang, Ruby, and Clojure languages.
• Suitable for applications that are expected to process high loads in millions of requests.
• It’s extensible to have developers define their own constructs as and when there’s a need.

Pros:

• Like Clojure, Elixir also supports immutability, which makes it ideal for multi-threaded applications.
• Can create highly concurrent and scalable applications that are highly fault-tolerant.

Cons:

• Overall reliability of application is high, but writing code in Elixir compared to other high-level languages like Java is quite tricky.
• Since its open-source, the only support is community forums which are still young and growing.
• It’s difficult to test – especially Unit test elixir apps.

Website: Elixir

#3) Haskell

Best for Haskell is used for applications that are required to be highly performant since the Haskell compiler is great at optimization.

It’s an advanced functional programming language that can create declarative statically typed code.

Features:

• Statically typed i.e it’s a compile type language and throws a compiler error in case of incorrect syntax.
• The type is inferred bidirectionally.
• Chain of functions with lazy loading.
• Great for concurrent multithreaded programming – contains several useful concurrency primitives.

Pros:

• Open sourced and a lot of community-created packages/libraries are available for use.
• Highly expressive and concise syntax.

Cons:

• Steep learning curve.
• Not used for normal web applications or real-time applications – mostly preferred for concurrent and scalable applications.
• Programs look cryptic and are a little tough to understand.

Website: Haskell

#4) Scala

Best for combining best of both static and dynamic languages. People coming from Java backgrounds might find Scala a little easy to learn.

Used for building data pipelines and big data projects.

Scala language combines OOP and functional programming in a single packaged High-level language. It supports JVM and Javascript runtimes, which allow both strict type checking of Statically typed language and the support of these runtimes allows Scala to leverage the existing ecosystem of libraries.

Features:

• Seamlessly interoperable with Java
• Statically typed features help in type inference and check the type errors at compile time.
• Fully functional programming with functions as first-class objects – can be called, assigned, or passed to another function.

Pros:

• Good IDE support.
• Objects are inherently immutable, which makes them a good choice for concurrent programming.
• Easy to pick up and learn.

Cons:

• Being a hybrid of OOPs and functional programming, it makes type information a little bit harder to understand.
• Has currently has a limited developer pool and hence limited community forums and support.

Website: Scala

#5) Python

Best for teams having a lot of data science or machine learning projects to be quickly onboarded should consider using Python.

Python is a general-purpose programming language that lets you build stuff quickly. With its easy-to-read and understand syntax, Python has become a language of choice for almost all the data pipeline and Machine learning-related work.

Features:

• Interpreted and dynamically typed language.
• Portable language – write once and run many.
• Object-oriented programming language.

Pros:

• With its widespread adoption, it has huge community support with a large ecosystem of libraries available for use.
• With Python, you can also build GUIs using libraries like – Tkinter, JPython, etc.
• Python is extensible – i.e. you can easily extend it with C/C++/Java code.
• Programming using Python is 5-10 times faster as compared to older languages like C/C++.

Cons:

• Dynamic typing might lead to errors that are not caught until the script is executed. The interpreted nature could result in leaving the scope of defects getting to production unnoticed.
• Due to its interpreted nature, it has its speed limitations.

Website: Python

#6) Elm

Best for teams looking to create reliable web applications with a functional programming language should consider using Elm.

Elm is a functional programming language for building HTML apps. It makes the apps render extremely fast with a well-architected framework.

Features:

• Have an intelligent compiler making refactoring easy and fun.
• With its own virtual DOM implementation, the applications built using this framework can render extremely fast.
• Provides interoperability with Javascript.

Pros:

• Highly readable and user-friendly compile-time error messages.
• Everything is immutable in Elm.
• Doesn’t have run time exceptions or null values – The type checking ensures that your domain is modeled completely and carefully.

Cons:

• Lack of good documentation – The adoption is really small and hence limited community support.

Website: Elm 

#7) F#

Best for people familiar with C# syntax and concepts and who want to move to functional programming can consider choosing F#.

F# is an open-sourced, cross-platform programming language for writing robust and performant code. F# follows a data-oriented functional programming paradigm that involves transforming data with the help of functions.

Features:

• It has a lightweight and easy-to-understand syntax.
• Immutable objects make it a good choice for multithreaded applications.
• Pattern matching and async programming.
• Rich set of data types.

Pros:

• Simple code with data-oriented design.
• Superset of C#.
• Full type safety – all the declarations and types are checked at the compile time.

Cons:

• Cyclic dependencies or circular dependencies need to be defined accurately.

Website: F#

#8) Erlang

Best for using for messaging-based applications like Chat apps, Messaging queues, or even blockchain apps. Hence, teams building such apps can consider using this language.

Erlang is used to build huge scalable real-time applications which are required to be highly available. Some domains where it is heavily used are telecom, instant messaging, and banking applications.

It was built around the 1980s at Ericsson for handling telephone switching systems.

Features:

• Process-oriented – it uses lightweight processes which communicate with each other via messages.
• Fully functional with support for pure functions and higher-order functions.
• Storage management is automated and garbage collection is implemented on a per-process basis, which helps in building highly responsive applications.

Pros:

• Well-documented libraries.
• Can help to build highly concurrent, scalable, and reliable applications.
• A small set of syntax primitives makes it simple.
• Mature community of developers and is under active development and collaboration.

Cons:

• Deploying Erlang applications can be cumbersome – mostly due to the lack of a proper package manager.
• Dynamically typed – hence compile-time checking of code is not possible.

Website: Erlang

#9) PHP

Best for using for quick prototyping and web development with minimal code as well as for creating Web-based Content Management Systems.

The name PHP stands for Hypertext Processor. It’s a general-purpose scripting language that is mostly used for web development. It powers some of the most widely used web platforms, like WordPress & Facebook.

Features:

• Interpreted language.
• Simple & easy to use.
• Flexible as it can be embedded with HTML, JavaScript, XML, and many others.
• Supports a few OOP features from PHP 4 onwards.

Pros:

• Free & open source.
• Platform Independent which enables it to run on any OS.
• Simple and easy to implement.
• Powerful library and significant community support.

Cons:

• Isn’t very secure.
• Lack of dedicated libraries for modern applications – PHP lacks support for newer technologies like Machine learning and Data science as compared to other scripting languages like Python.
• No static compilation can lead to type errors.

Website: PHP

#10) Javascript

Best for interactive front ends – Plain Javascript is rarely used but can be helpful for quick prototyping.

It’s a lightweight interpreted programming language with functions as first-class constructs. Standards for Java are defined by ECMAScript.

Features:

• Lightweight and interpreted – thereby offering greater speeds.
• Highly popular for building front ends for web applications.
• Easy to understand and learn.

Pros:

• Can be used for both FE applications with frameworks like AngularJs, React, as well as server-side applications through frameworks like Node JS.
• Great community support due to widespread adoption.

Cons:

• The biggest con is client side security issue as the code is viewable to users in web applications.
• Another issue is rendering at times as different browsers interpret it differently.

Website: Javascript

#11) Java

Best for teams looking for developing standard enterprise application backends with a single computer as well as distributed across servers with excellent support over most cloud platforms.

Java is one of the most widely used languages primarily for developing backend applications. It has existed for 2 decades and is used by more than 12 million developers worldwide.

Features

• General purpose, High level, and OOP language.
• Platform independent.
• JDK provides the development environment and basic libraries while JRE is platform-specific runtime environment for Java-based applications.
• Automatic memory management and supports multi-threading.

Pros:

• Wide community as it’s the most used programming language in the world.
• Platform dependent – Write Once and Run anywhere.
• Supports distributed system and programming.

Cons:

• Memory management is automatic, but when garbage collection is done, other active threads are stopped, which can impact application performance at times.
• No or less support for low-level programming in Java.

Website: Java

#12) C++

Best for teams looking for building real-time applications having support for OOPs as well as memory management and that can run on limited resources.

C++ is a general-purpose programming language that was developed by Bjarne StroutStrup in 1979.

Features:

• Widely used in Operating System development, real-time applications, high-frequency trading applications, IOT, etc.
• Supports all OOPs features.
• Can run on multiple platforms like Windows, Linux, macOS.

Pros:

• It’s a kind of Mid Level language – it supports both low-level programming and Object-Oriented Programming.
• Supports dynamic memory allocation – which helps to free up and allocate memory – hence giving full control to programmers for memory management.
• Fast and Powerful – It’s a compiler-based language that doesn’t need a special runtime in order to be executed.

Cons:

• Programs are a lot verbose as compared to other high-level languages like Java and C#
• Inefficiently done memory cleanup might result in less performant programs.

Website: C++

#13) Idris

Best for teams looking for prototyping and researching using type-driven development.

Idris encourages Type driven development, where types are tools to construct or plan the program and use a compiler as a type checker.

Features:

• Dependently typed language.
• Supports views for pattern matching.
• Supports high-level programming constructs.

Pros:

• Type signatures can be refined or customized.
• The syntax can be extended using syntax extensions.
• Good for research prototyping.

Cons:

• Bigger learning curve.
• Limited adoption hence doesn’t have very wide community support.

Website: Idris

#14) Scheme

Best for scheme language that can be used for writing text editing applications, operating system libraries, financial statistics packages, etc.

Scheme is a general-purpose programming language. It is high level and supports Object-oriented development as well

Features:

• Scheme language was evolved from Lisp Programming language hence inheriting all the features of Lisp.
• Rich set of data types and flexible control structures.
• Allows programmers to define syntactic extensions.

Pros:

• Simple syntax hence easy to learn.
• Supports Macros as well as integrated constructs.
• Used for teaching programming concepts to newcomers.

Cons:

• Doesn’t offer full-fledged support for development like Multithreading and Advanced constructs like Lambdas etc compared to languages like Java.
• Doesn’t offer full compatibility across various versions.

Website: Scheme 

#15) Go

Best for GoLang is used for programming scalable and distributed applications that are highly responsive as well as lightweight.

Go is a general-purpose programming language that was designed originally by Google. It has become one of the leading modern programming languages amongst the developer community.

Go language is used for a lot of DevOps-related automation. As a matter of fact, a lot of popular infrastructure tools like Docker and Kubernetes are written in Go

Features:

• It’s statically typed, which helps in compile-time type checking.
• Dependencies are decoupled, as Go has Interface types.
• Provides built-in functions for primitive types as well as standard packages for server-side programming.

Pros:

• Go is simple to learn and understand.
• Used to build highly scalable and performant applications.
• Testing support is built into the standard library itself.
• Easy concurrency model – helps build multithreaded applications with ease.

Cons:

• Doesn’t have support for Generics, which is a standard feature in most of the OOP languages like Java, C#, etc.
• Doesn’t have very wide library support in comparison to other counterparts.
• The package manager’s support is not very reliable.

Website: Go

#16) Rust

Best for developing highly performant and scalable applications with safe concurrency handling support.

Rust performed similar to C & C++ and at the same type, ensuring code safety.
Rust has been used by popular applications like Firefox and Dropbox. It’s gaining traction and a lot of popularity in recent times.

Features:

• Statically types programming language designed for performance and safety.
• Syntax is similar to C++ and is developed by Mozilla Foundation.
• Supports Generics with guaranteed type safety.

Pros:

• Great support for concurrent programming.
• Growing community and number of packages available to use.

Cons:

• Has a steep learning curve. Rust programs are complex and difficult to learn.
• Compilation is slow.

Website: Rust

#17) Kotlin

Best for becoming the de facto standard for Android Applications as it’s supported by Google for App development. It’s also gaining its adoption for building server applications as it’s completely interoperable with Java.

Kotlin is a statically typed open source programming language that is fully interoperable with Java. The Kotlin compiled code runs on JVM. Kotlin supports all functional constructs as well as it’s fully Object-oriented.

It was developed by JetBrains.

Features:

• Powerful and expressive – eliminates syntactic sugar and helps in writing concise code.
• Supported by Google for Android development and can now be used for iOS development as well.
• First-class support for functions.
• Type and Null safety supported out of the box.

Pros:

• Intuitive syntax.
• Widespread adoption leads to strong community support.
• Easily maintainable and has support across a lot of popular IDEs like Android Studio and Intellij Idea.

Cons:

• At times, compilation or build cleaning is slower as compared to Java.
• Still gaining adoption, hence difficult to find experts/professionals.

Website: Kotlin

#18) C#

Best for developing Web and Windows-based applications for the .NET platform and gaming applications using Unity game engine.

C# was developed in 2000 as a modern OOP language designed for developing Web and Windows-based applications for the .NET framework.

Features:

• Statically typed and easy to read.
• Highly scalable.

Pros:

• Great support for concurrent programming.
• Growing community and number of packages available to use.
• .NET platform is open-sourced via Mono platform, which can enable C# to be used for cross-platform applications.
• Widely used for game development using Unity engine.

Cons:

• C# is not portable. In the case of Web-based applications, it requires the program to be run on Windows-based servers.

Website: C#

#19) TypeScript

Best for all plain JavaScript apps can be built using typescript as it provides an easier compiled JavaScript code, thereby ensuring type checking and reducing development time with easy constructs.

Built by Microsoft, TypeScript is a strongly typed programming language built on top of Javascript. It adds additional syntax to JS which helps to have tighter integration with editors as well as introduce static type checking.

The compiled typescript file is nothing but plain JavaScript.

Features:

• Fully interoperable with JavaScript.
• Fully supports OOP concepts.
• Typescript can be used for DOM manipulation to add or remove elements similar to JavaScript.

Pros:

• Provides benefits of static type checking to JavaScript.
• Makes code more readable and structured.
• Helps detect common bugs at compile stage.
• Typescript finds rich support for common IDEs like Visual Studio Code, WebStorm, Eclipse, etc.

Cons:

• Bloated code due to extra syntax constructs.
• Extra step for running JavaScript – TypeScript code needs to be compiled or transpiled to Javascript before it can be executed.

Website: Typescript

#20) ReasonML

Best for helping you write simple and quality type safe code using both JavaScript and OCaml ecosystems.

Reason Programming language is a powerful, statically typed language leveraging JavaScript and OCaml programming environments. It’s widely used by a lot of top organizations like Facebook, Messenger, etc.

Features:

• Goal is to make OCaml integrated into the JavaScript ecosystem.
• Helps adding type checking to JavaScript providing more stability and confidence in the code.

Pros:

• Static type checking helps in reducing bugs and improving the refactorability of your code.
• The code is like Javascript, hence making it easy to learn and understand.

Cons:

• At times, the compilation can be slow due to statically typed code.

Website: ReasonML

#21) PureScript

Best for teams looking to have their pure JavaScript-based apps to have better readability and get the advantage of static type checking.

It’s a strongly typed functional language that compiles into Javascript. It can be used for both client-side and server-side development.

Features:

• Can be used to build real-world applications with functional techniques and expressive types.
• Supports Higher rank polymorphism and Higher kinded types.
• Compiler and package managers can be easily installed as node (NPM) package managers.

Pros:

• Has an independent package manager named Spago.
• Compiles to readable Javascript.

Cons:

• Has a steep learning curve.
• Not a wide community adoption.

Website: Purescript

#22) Swift

Best for building apps for Apple devices like MacOS, iPhone, and iWatch.

Swift was released by Apple in 2014 and is used to develop applications for Apple devices. Organizations building iOS apps use Swift as the programming language.

Swift was released by Apple in 2014 and is used to develop applications for Apple devices. Organizations building iOS apps use Swift as the programming language.

Features:

• General-purpose compiled programming language and supports all iOS Platforms like iPhone, iPad, and iWatch.
• Interoperable with Objective C.
• Supports Generics and Protocol extensions, making generic code even easier.
• Functions are first-class citizens.
• Ensures Null safety.

Pros:

• Simplified syntax helps in the Rapid development process.
• Approx 3.4x speedier than Objective C

Cons:

• Lack of support for older iOS versions (supports versions later than iOS7)

Website: Swift

Conclusion

In this tutorial, we learned about different functional programming languages that are most widely used.

Functional programming has existed for quite some time and is gaining quite a lot of popularity these days. It’s mostly used to build applications that are required to handle large amounts of concurrent load and be highly performant with very low latency.

The code written in Functional Programming is usually short and succinct, but at times it can get complex to understand what the code might be doing. Some of the commonly used languages are Scala, Rust, Go, Haskell and Erlang.

Most of the newer Object-oriented programming languages like Kotlin, Java, etc are also catching up with support for Functional programming paradigms.