The Clojure Koans are a fun and easy way to get started with Clojure - no experience assumed or required. Just follow the instructions below to start making tests pass!
The easiest and fastest way to get the koans up and running is to download the latest zip file from Github. This way, you'll have all the dependencies you need, including Clojure itself and JLine, and you can skip the rest of this section (skip to "Running the Koans").
If you're starting from a cloned or forked repo, that's cool too. This way you'll be able to track your progress in Git, and see how your answers compare to others, by checking out the project's Network tab. You might want to create your own branch - that way if you pull back the latest koans from master, it'll be a bit easier to manage the inevitable conflicts if we make changes to exercises you've already completed.
You have a few options for installation:
- Install the dependencies for the koans (such as Clojure) on your machine,
- Use Vagrant and the configuration in this repository
- Use Docker
Instructions for each option are below!
Installation on Your Machine
The only things you'll need to run the Clojure Koans are:
- JRE 1.6 or higher
You can use Leiningen to automatically install the Clojure jar in the right place. Leiningen will also get you a couple more jarfiles, including JLine, which allows you some of the functionality of readline (command-line history, for example).
Dependencies are installed automatically with lein 2, but if for some reason you're on lein 1 and can't upgrade, you'll need to run
which will download all dependencies you need to run the Clojure koans.
I strongly recommend that you upgrade to lein 2 instead!
Installation with Vagrant
vagrant up vagrant ssh cd /vagrant lein koan run
Installation with Docker
Once you've got Docker installed, you're basically all set. You can run these commands to get started:
To run koans:
docker run --rm -it -v $(pwd):/app -w /app clojure lein koan run
To execute REPL:
docker run --rm -it -v $(pwd):/app -w /app clojure lein repl
Running the Koans
If you're running from the zipfile, simply run
script/run on Mac/*nix
script\run on Windows
If you're running from a checkout using lein 2, run the koans via
lein koan run
If want to run directly from a REPL, once you are inside the
lein repl prompt you can run the koans with
It's an auto-runner, so as you save your files with the correct answers, it will advance you to the next koan or file (conveniently, all files are prefixed with the sequence that you should follow).
You'll see something like this:
Now meditate on /home/colin/Projects/clojure-koans/src/koans/01_equalities.clj:3 --------------------- Assertion failed! We shall contemplate truth by testing reality, via equality. (= __ true)
The output is telling you that you have a failing test in the file named
01_equalities.clj, on line 3. So you just need to open that file up and make
it pass! You'll always be filling in the blanks to make tests pass.
Sometimes there could be several correct answers (or even an infinite number):
any of them will work in these cases. Some tests will pass even if you replace
the blanks with whitespace (or nothing) instead of the expected answer. Make sure
you give one correct expression to replace each blank.
The koans differ from normal TDD in that the tests are already written for you, so you'll have to pay close attention to the failure messages, because up until the very end, making a test pass just means that the next failure message comes up.
While it might be easy (especially at first) to just fill in the blanks making things pass, you should work thoughtfully, making sure you understand why the answer is what it is. Enjoy your path to Clojure enlightenment!
Trying more things out
There's a REPL (Read-Evaluate-Print Loop) included in the Clojure Koans. Just run:
script/repl on Mac/*nix
script\repl on Windows
If you're on lein 2,
lein repl is what you want instead.
Here are some interesting commands you might try, once you're in a running REPL:
(find-doc "vec") (find-doc #"vec$") (doc vec)
And if those still don't make sense:
(doc doc) (doc find-doc)
will show you what those commands mean.
You can exit the REPL with
CTRL-d on any OS.
Patches are encouraged! Make sure the answer sheet still passes
lein koan test), and send a pull request.
The file ideaboard.txt has lots of good ideas for new koans to start, or things
to add to existing koans. So write some fun exercises, add your answers to
resources/koans.clj, and we'll get them in there!
Please follow the guidelines in http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html for commmit messages, and put your code in a feature branch (not master) before making the pull request. This makes patches easier to review.
Feel free to contact me (Colin Jones / trptcolin) on Github or elsewhere if you have any questions or want more direction before you start pitching in.
These exercises were started by Aaron Bedra of Relevance, Inc. in early 2010, as a learning tool for newcomers to functional programming. Aaron's macro-fu makes these koans extremely simple and fun to use, and to improve upon, and without Relevance's initiative, this project would not exist.
The use and distribution terms for this software are covered by the Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) which can be found in the file epl-v10.html at the root of this distribution. By using this software in any fashion, you are agreeing to be bound by the terms of this license.