This year, I decided to use Advent of Code to learn the language Swift. Since there were only 12 days of tasks for 2025, here is my summary of experiences. Also check out my solutions.
Tooling
I used Swift 6.2 on Void Linux, which I compiled from scratch since there were no prebuilt binaries that worked with a Python 3.13 system (needed for lldb). It’s possible to bootstrap Swift from just a clang++ toolchain, so this wasn’t too tedious, but it still required looking up Gentoo ebuilds how to pass configuration properly. As an end user, this should not worry you too much.
Tooling in general is pretty nice: there’s an interpreter and you can run simple “scripts” directly using swift foo.swift . Startup time is short, so this is great for quick experiments. There’s also a REPL, but I didn’t try it yet. One flaw of the interpreter (but possibly related to my setup) is that there were no useful backtraces when something crashed. In this case, I compiled a binary and used the included lldb , which has good support for Swift.
There’s also a swift-format tool included to format source code. It uses 2 spaces by default, but most code in the wild uses 4 spaces curiously. I’m not sure when that changed.
Since I only write simple programs using a single source file, I didn’t bother looking at swift-build yet.
By default, programs are linked dynamically against the standard library and are thus super compact. Unfortunately, many modern languages today don’t support this properly. (Statically linking the standard library costs roughly 10MB, which is fair too.)
The language
In general, the language feels modern, comfy, and is easy to pick up. However, I found some traps as well.
The syntax is inspired by the C family and less symbol-heavy than Rust’s. There’s a block syntax akin to Ruby for passing closures.
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