Solve the 2022 Advent of Code Puzzles with OCaml

by Christine Rose on Nov 24th, 2022

Too many programmers only know OCaml through a functional programming language overview course at university. They erroneously believe OCaml is used primarily in academia rather than in the real world. Not only is OCaml already used in several prominent businesses, it can also be used for fun projects, like the upcoming Advent of Code.

What is Advent of Code?

Advent of Code is an annual online Advent calendar produced specifically for programmers. It publishes a series of daily puzzles, revealing a new puzzle every day from 1 December to 25 December. That's 25 days of coding challenges! These puzzles can be solved in the language of your choice.

Every year they have new puzzles and anyone can participate, whether you're new to programming or a veteran. Advent of Code has been running since 2015 and has attracted a large community of developers around the world!

It's not only a fun way to learn new languages, but it also provides a great way to meet new people with the same interests and exchange ideas.

OCaml 5 is set for release later this year, so it's a perfect time to learn and practice OCaml with Advent of Code!

5 Reasons to Learn OCaml

There are so many misconceptions around OCaml that it's hard to know where to start. Basically, OCaml can do what Python, C++, Java, or any other major programming language can do. Here are a few specific reasons why OCaml should be the next language you learn:

1. Secure-By-Design

Cyber attacks have become more commonplace and sophisticated, so security has become a top priority in software development. With the proliferation of cloud services and Internet-connected devices, software must be secure-by-design to prevent malicious actors from taking advantage of any bugs or loopholes. Creating software with a secure-by-design language like OCaml helps meet this goal.

OCaml has built-in features and design patterns, like type and memory safety, that make it secure-by-design.

2. Performant Garbage Collector

Contrary to popular belief, OCaml's garbage collector (GC) doesn't slow things down because it's incremental, which can help avoid the problems of manual memory management in large or long-running programs.

OCaml's GC has to run periodically, but it can do so in small incremental steps. Although allocations that trigger a GC are longer than a malloc call (used in C), most of them are almost immediate because allocating from the minor heap is as cheap as allocating on the stack.

This incremental GC avoids the problems normally associated with garbage collection, like tying up memory and slowing down the process.

3. Confidence in the Code Through Type Checking

OCaml's compile-time type checking eliminates many potential runtime errors, and its strong type inference eliminates several redundant type annotations. Often, a programming language has either type safety or type inference, but with OCaml you get both!

4. Multicore!

With the release of OCaml 5 later this year comes Multicore support! Multicore is an extension of OCaml with native support for Shared-Memory Parallelism through domains and Concurrency through algebraic effects. The ability to run OCaml on multiple cores will make it even faster than before.

5. Extensive Tools & Libraries

OCaml has some great tools and helpful libraries, like MirageOS, Irmin, and so many others as reported by seasoned OCaml programmers in this Discuss thread.

OCaml platform tools include the Dune build system, opam package manager, Merlin IDE, and the odoc documentation generator.

Pro Tip: Learn OCaml Basics First

Before you start solving puzzles, learn the basics to ensure you understand the most common data structures and algorithms. It's important to know how to print to the console, read and write files, and parse text.

It’s also a good idea to read about common problem-solving approaches. For example, checking whether a solution is correct is a crucial part of the solving process. This will help you understand the challenges better, and you can save yourself a lot of time and frustration.

Get Up & Running with OCaml today through the tutorials on Also consider joining the OCaml Community Forum Discuss. They're very welcoming of those new to OCaml as well as experienced OCaml programmers, and members will quickly answer any questions you have while you learn.


The Advent of Code is a great way to practise your problem-solving skills in a new programming language during the holidays.

Give OCaml a try this holiday season. You won't regret it!

Learn more about the forthcoming OCaml 5 through KC Shivaramakrishnan's Keynote Address and speaker deck. Stay tuned to this blog for release updates and a series of posts about why you should consider OCaml as your next language.