Choosing Elegance: The Case for F# in Application Development

This post is for Day 6 of F# Advent Calendar.

We all know the go-to languages for most companies in application software development: Java, C#, TypeScript, and Python, to name a few. There's obviously nothing wrong with using these ubiquitous languages, but there's a tendency to overlook the potential of others. In contrast to this narrow view, a strong case exists for considering a variety of alternative languages. Particularly for F#, which I will focus on in this article, there's a compelling argument to be made. Why is F# often sidelined, and why does it deserve more attention in the realm of serious application development? Let's dispel some common misconceptions and explore the untapped potential of F#.

Practical for Applications

F# is often unfairly pigeonholed as merely a language for data science, web crawlers, or domain-specific languages (DSLs). This is similar to being remembered only as a child by a distant relative who hasn't seen you grow up - just based off of an idea that seems concrete but reality is much different. Such a narrow view overlooks F#'s versatility and practicality in typical application development, including areas like UIs, APIs, microservices, and scripts. Just like Java and C#, F# has its strengths and unique features that make it a formidable choice for these applications. Let's delve into a few areas where F#'s practicality particularly shines.

The Full Power, Performance, and Scalability of .NET

F# harnesses the full power, performance, and scalability of the .NET framework, making it a formidable choice for modern application development. This integration means F# enjoys compatibility with the entire suite of .NET libraries, benefiting from the continuous performance enhancements in each .NET release. This compatibility is a significant advantage, as it ensures that any application achievable with C# is equally feasible with F#. For instance, consider the AWS CDK library for .NET, typically used with C#. In F#, this library can be utilized to define your AWS infrastructure with significantly less code, showcasing F#'s efficiency and conciseness. This example underlines the versatility and power F# brings to the table, thanks to its seamless integration with .NET.

Correctness and Fearless Refactoring

Experiencing the type safety of F# is a revelation, particularly when contrasted with other type-safe languages. Idiomatic F# promotes type-driven development and utilizes discriminated unions for domain modeling, leading to compiler-enforced business logic handling. This approach ensures exhaustive checking for every possible scenario, a feature deeply rooted in the design principles of ML-based languages. Understanding the influence of ML on F# helps appreciate why extolling its type safety is not just a favorable opinion but an intrinsic, game-changing fact. This becomes especially evident when you compare it to languages like C#, where certain complex scenarios might not be as seamlessly handled. Once you’ve experienced this in F#, it's hard to look at type safety in other languages the same way.

Consider a startup scenario: often, your understanding of the domain evolves, revealing that initial assumptions were off-mark. Invariably, this leads to refactoring, which can be daunting. Traditional approaches might lead to partial or complete rewrites, depending on the modularity of the application and whether it's a monolith or consists of micro services. However, with F#, a second "bite of the apple" comes with less dread.

F#'s superior type safety and algebraic type system offer a higher confidence level when refactoring, especially compared to refactoring in highly polymorphic, OOP-centric systems. The clarity and predictability of F#'s type system reduce the risks typically associated with major code alterations. Refactoring in F# feels more like a controlled evolution of your application rather than a precarious overhaul.

Simplicity as an Idiom

F# is a language that's intentional about its ergonomics. Don Syme, the language's BDFL, often turns down features that add unnecessary complexity to the language. The language is designed to be delightful, yet correct. Simple, yet robust. Developers transitioning from heavily OOP-centric languages might initially cling to familiar patterns, whether they’re from the Gang of Four or more modern architectural schools of thought. However, F# invites you to let go of this complexity. This transition might feel unfamiliar at first, but soon you’ll discover that even in complex applications, the combination of two simple concepts - functions and types - is often all you need to achieve what you'd use a fancy design pattern for in an OOP codebase.

This idiom of simplicity profoundly impacts application development. When building applications – even those that could be developed in C# or Java – the cognitive load in F# is noticeably lower. Even if you are using libraries that are available in C#, consuming them in F# benefits from its inherent simplicity and clarity. The reduced mental overhead in managing and scaling applications means more resources are available for developing new features. In practical terms, this translates to faster development cycles, easier maintenance, and the ability to focus more on innovation rather than grappling with complexity.

Scaling the Team

Hopefully, by now, I've shown that F# has a unique set of attributes that make it particularly practical for application development. The language is designed for ergonomics, simplicity, and correctness. It highlights the domain with its type system - an underestimated yet significant benefit - after all, software that doesn't represent the domain is useless. On top of all that, it has access to one of the best ecosystems as a .NET language.

There is one ”impracticality” that I haven't addressed, and that's the idea that you won't be able to scale your team because F# doesn't have as large of a community as other languages. While it's true that there are not as many F# developers as the most popular languages, I believe it is a fallacy for this to be the main reason not to use it. To this, I have a philosophical response:

A developer's value is not solely in their current knowledge, but in their capacity to learn and adapt. The ability to embrace new languages and paradigms is a hallmark of a great developer. In the case of F#, finding developers who are eager to learn and immerse themselves in the language can be more valuable than hiring someone with expertise in a more common language but a fixed mindset. The F# community, though smaller, is known for its enthusiasm and supportiveness. This vibrant community provides an excellent environment for new learners to quickly become proficient and even passionate about F#.

Furthermore, the notion of a language's community size being directly proportional to its viability for scaling a team is somewhat misleading. Quality over quantity applies here; a smaller, more dedicated group of F# developers can be more effective and innovative than a larger, less engaged group in another language. Also, many experienced developers who have not had the chance to use F# professionally may jump at the opportunity to do so, bringing with them a wealth of general programming experience and a fresh perspective to F# development.

The key to scaling a team effectively is not just about numbers, but about fostering a culture of learning and passion for the craft. An engineer willing to learn and grow with the language is an asset, and with F#'s robust features and supportive community, scaling your team becomes not only feasible but also an opportunity to build a uniquely skilled and enthusiastic workforce.


The conventional reliance on mainstream languages overlooks a wealth of formidable alternatives, among which F# stands out as a particularly compelling choice in application development. Its strengths in ergonomics, simplicity, and correctness, coupled with the robustness of the .NET ecosystem, elevate it beyond a language for niche applications, making it suitable for a diverse array of software development needs. The misconceptions about F#'s impracticality, especially regarding team scaling, reflect an outdated perspective rather than the language's true capabilities. F#'s adeptness at representing complex domains with clarity, along with its enthusiastic and supportive community, transforms it into a language that not only streamlines application development but also cultivates a culture of continuous learning and passion. As the software industry evolves, adopting languages like F# that blend technical excellence with a vibrant community spirit becomes increasingly essential. For those willing to look beyond conventional choices, F# offers a refreshing and powerful toolkit for crafting modern, scalable, and maintainable applications. In a world in need of more beauty, F# contributes not just with its technical elegance, but with an ethos that enriches the entire software development landscape.