Functional programming languages: a blazingly fast face-off

While object-oriented programming has dominated enterprise development for decades, a quiet revolution has been brewing. Functional programming languages, once relegated to academic circles, are now powering the infrastructure of companies like Netflix, Twitter, and Goldman Sachs. As systems grow more complex and concurrent, the immutable data structures and mathematical foundations of functional languages are proving to be not just elegant but essential.

The question isn't whether functional programming will become mainstream – it already has. JavaScript, the world's most widely used programming language, has adopted first-class functions, as well as map, filter, and reduce operations – all borrowed from functional programming. Python, despite being a multi-paradigm language, includes lambda functions, list comprehensions, map, filter, and reduce as core features, making functional programming approaches accessible to millions of developers.

The question is which language will best serve your specific needs. And we’ve gathered here to unpack exactly that.

Clojure

The descendant of the Lisp pioneering arcane arts of lambda calculus, Rich Hickey’s mind child – Clojure – is cherished for its superior data handling philosophy. Well, as a Clojure development company for over 10 years, we may be biased here, but seriously, we have reasons. Clojure treats code as data and data as the primary citizen of your program. As an applied approach, it makes complex data transformations the main focal point of the development process and, consequently, the primary asset of the solution. 

Being run on JVM, Clojure gives you access to decades of Java libraries – it’s a nice breeze up here on the giant’s shoulder – while skipping Java’s wrestling with objects. On top of that, with JVM, Clojure skips Lisp’s portability issues, or one-third of the so-called “Lisp’s curse”.

Why people love it

In three words, Clojure is interactive, data-driven, and concurrent, making it a powerful tool for handling large volumes of data. It’s concise and, again, interactive, so rapid prototyping with it is truly rapid.

Previously, we discussed 10 business benefits of choosing Clojure as your tech stack. To summarize, Clojure’s business impact is:

• Faster time-to-market
• Lower bug rates
• Easier maintenance
• Great flexibility

Clojure’s niche

1. Financial services
   Complex business rules, risk calculations, and real-time trading systems

2. Data engineering
ETL pipelines, data streaming, and analytics platforms

3. Web APIs
Especially those requiring complex data manipulation

4. Exploratory programming
When you're not sure what you're building yet

Looking through a list of Clojure companies, you’ll find the abovementioned pattern: they're either handling massive scale (Netflix, Walmart), complex financial logic (Nubank, Griffin), or cutting-edge data problems (Rama, Metabase). The noticeable tendency here is that they're solving problems where data complexity and system reliability matter more than having a huge pool of available developers.

Elixir

You may have heard about Pinterest, Discord, and Toyota using Elixir; we covered that in our previous article. However, the reason behind this technical decision is what concerns us today: the combination of BEAM under the hood and Ruby-inspired syntax results in a powerful brew of technical capabilities and an exceptional developer experience.

Why people love it

Elixir is a distributed, resilient and concurrent programming language. It’s so resilient that you can just Let It Crash, which offers a particular way of thinking about solution building: instead of defensive programming, you build systems that can recover gracefully from failures. The Actor model makes concurrent programming intuitive, while pattern matching makes code both readable and robust.

Elixir’s niche

1. Real-time applications
   Chat systems, live updates, collaborative tools
2. High-traffic backends
   APIs that need to handle thousands of concurrent users
3. IoT and embedded systems
   Devices that can't afford to go offline
4. Financial systems
   Payment processing, where downtime costs money

Haskell

Haskell is the mathematician's dream language – pure, elegant, and uncompromising in its functional approach. Named after logician Haskell Curry, it's where functional programming theory meets practical application, though "practical" here requires some qualification. Outside the community, Haskell is known for its strong ties to academia and hence, its concepts permeating the programming space. It’s also known for its adepts' unwavering devotion.

Why people love it

Haskell is pure, lazy and type-safe. Its type system is so sophisticated that "if it compiles, it works" isn't a mere meme. Lazy evaluation means you only compute what you need, when you need it, enabling elegant solutions to complex problems. The purity forces you to think differently about program structure, leading to more predictable and maintainable code.

The language's mathematical foundations make it particularly suited for domains requiring high correctness guarantees. When Facebook needed to analyze billions of anti-spam rules, they chose Haskell. When you need to be absolutely certain your code is correct, Haskell's type system becomes your ally.

Haskel’s niche

1Financial modelingRisk analysis, derivatives pricing, algorithmic trading2Compiler constructionGHC itself is written in Haskell3Academic researchLanguage research, theorem proving4Domain-specific languagesCreating embedded DSLs for specific problems

Scala

Scala attempts to bridge two worlds: the object-oriented familiarity of Java and the functional programming power of languages like Haskell. Created by Martin Odersky, it's designed to be a "better Java" while gradually introducing functional programming concepts. According to the Stack Overflow 2024 Survey, there are 2.6 percent active users (compared to Java’s 30.3 percent).

Why people love it

Scala is expressive, scalable, and pragmatic. It runs on the JVM, providing access to Java's ecosystem while offering a more concise syntax and powerful functional features. The language scales from simple scripts to complex distributed systems (hence the name "Scala" – scalable language).

Pattern matching, case classes, and immutable data structures make the functional programming approach accessible to developers coming from an imperative background. At the same time, you can still write object-oriented code when it makes sense. This flexibility has made Scala the language of choice for companies transitioning from Java, as they seek the benefits of functional programming.

Scala’s niche

1. Big data processing
   Apache Spark, Kafka, and Akka are all written in Scala
2. Real-time streaming
   Twitter uses Scala for streaming API, storage systems, and geo services
3. Financial services
   Morgan Stanley and Goldman Sachs rely on Scala for trading systems
4. Machine learning platforms
   Netflix uses Scala for ML-based recommendation systems and search algorithms
5. Data engineering
   LinkedIn processes millions of concurrent data transactions using Scala with Apache Kafka

The production stories speak for themselves. Twitter partially switched from Ruby to Scala for better performance and reliability of their long-lived servers. Airbnb built its financial reporting pipeline in Scala, leveraging its fault tolerance and type system for horizontal scaling. Netflix utilizes Scala to develop stable APIs that underpin their recommendation engine and interactive experimentation platforms.

What's remarkable is the diversity of companies using Scala in production: from entertainment giants like Disney Streaming and Spotify, to tech companies like Apple and Microsoft, to financial institutions like PayPal and Stripe. Even LEGO uses Scala. This has become the pragmatic choice for any team that wants to leverage the benefits of functional programming without abandoning its Java ecosystem.

Takeaway

The future belongs to languages that can handle complexity gracefully, and functional programming languages are leading that charge. The functional programming paradigm is beyond just an academic exercise – it's a practical approach to building more reliable, maintainable, and scalable systems.

Each functional language has carved out its territory in the programming landscape. Financial services often gravitate toward Clojure and Haskell due to their mathematical foundations. Real-time systems choose Elixir for its fault tolerance. Big data platforms usually prefer Scala due to its JVM interoperability and paradigmatic flexibility. Whether you choose the data-driven elegance of Clojure, the fault-tolerant concurrency of Elixir, the mathematical purity of Haskell, or the pragmatism of Scala, you're investing in a programming approach that treats functions as first-class citizens and immutability as a feature, not a limitation.

If this functional programming world sounds dazzling to you, you're in good company. Our team of FP connoisseurs has been crafting elegant solutions with these languages for over a decade. Whether you're ready to dive in or just curious about what functional programming could do for your project, drop us a line. Let's explore how to transform complexity into elegance.