Folding Away Mutations in F#

I’ve been working in F# lately, and one of its smaller features has had a big impact on my programming style: Variables are immutable by default. If you want to change something, you have to declare it mutable. Sometimes, this is what I naturally reach for, and the language rubs my nose in it. Here’s […]

An Introduction to Property-Based Testing with JavaScript

Property-based testing is a powerful technique that’s been widely and successfully applied to functional-style codebases for a long time. As functional programming continues to get more and more popular among JavaScript developers, the value of this style of testing is becoming more obvious to a wider audience.

A Simpler Case for Functional Programming & “Elegant” Code

A lot has been written about the benefits of functional programming, but little of it is accessible to a newcomer. Some of the benefits are easy to understand from an inexperienced perspective (e.g. “it makes concurrency easier”), but others are pretty nebulous. Chief amongst the inscrutable properties of functional programming is its “elegance.” It isn’t […]

Using Decorators to Declaratively Extend Functions

The decorator pattern gained fame in the object-oriented world after being featured in the classic 1994 Gang of Four book, Design Patterns. Since then, it’s been used extensively in traditional object-oriented programming as an alternative to inheritance. What’s really going on behind the scenes though, is composition, which means decorators are also great for cleaning […]

4 Tips for Thinking Functionally

I’ve written before about why I prefer a functional programming paradigm to an object-oriented one, but it’s taken a long time to get there. I dabbled on and off for half a decade before the core ideas behind Clojure and Haskell really sank in and I could write code in my head without having to […]


REPLs (Read-Eval-Print-Loops) are often billed as a great place to experiment and learn a language or a framework. They provide a very tight feedback loop. However, it can be difficult or time-consuming to extract the knowledge gained from a REPL and include it in your source code. I’ve hit the up arrow many times in […]