exlings: learn elixir by breaking it

I maintain a small project called exlings, and this post exists because I would like you to try it and tell me where it hurts.

The idea is stolen, as all good ideas are. rustlings and ziglings proved the format: you learn a language by fixing small broken programs, one at a time, in order, with the compiler as your teacher. Not by reading about the language. Reading gives you recognition; the exercises give you recall. Only one of those survives a job interview.

exlings is that, for Elixir.

how it works

You clone the repo, run mix deps.get, then:

mix exlings

You get the first pending exercise. It is a small .ex file with something wrong with it: a missing piece of syntax, a pattern that doesn’t match, a function clause with a hole in it. You open the file, you fix it, you run mix exlings again. Green, next exercise. That is the entire loop, and the entire loop is the point.

If you don’t want to re-run the command manually, mix exlings.watch re-runs the current exercise every time you save. If you get stuck, mix exlings.hint gives you a hint, and the hints are progressive: the first one nudges your thinking, the last one nearly writes the answer, and each failed attempt reveals the next one automatically. Stuck is a state, not a failure. mix exlings.list shows progress, mix exlings.reset wipes it for when you want to suffer from the beginning again.

There is no IDE plugin, no web UI, no account, no streak counter. It is a Mix project and some tasks. The barrier to entry is having Elixir installed.

what it teaches

The exercises walk through the language roughly in the order you’d trip over it in your first months: values and the basic data structures, then pattern matching (including the pin operator, which is where everyone has their first oh, THAT’s what Elixir is moment), functions and guards, the pipe, Enum, recursion done properly with accumulators and tail calls, comprehensions, and the parts of strings and binaries that surprise people, like charlists, so the ~c"hello" jump scare gets defused in an exercise instead of in production. The track keeps growing toward processes and OTP, which is the reason we’re all here.

who it’s for

Beginners. People coming from another language who keep writing Elixir that looks like their old language with worse syntax highlighting. People who read the getting-started guide twice and still freeze in front of an empty file. It assumes no prior Elixir, no Erlang, no OTP. It does assume you can open a terminal, which I maintain is the one irreducible prerequisite of the entire profession.

It is also, quietly, for mentors: if you’re teaching someone Elixir, hand them the repo and let the watcher do the tedious part of feedback while you do the interesting part.

try it

git clone https://github.com/zoedsoupe/exlings
cd exlings
mix deps.get
mix exlings

Then tell me: where did you get stuck, which hint was useless, which exercise is broken in a way I didn’t intend (a bold claim for a project whose entire premise is intentional breakage, but here we are). Issues and PRs are open, exercises are easy to contribute, and the format makes reviews fast.

The best compliment the project has received so far is someone saying they forgot they were learning. Go break something. Then fix it. That’s the whole job, it turns out.