I’m not going to talk about the language, or its philosophy, or its pitfalls or best practices, or any of that. I’m going to talk about the most significant, but least expected, barrier to learning Clojure: workflow.
It took me a while to work out how to work with Clojure.
Everyone bangs on about the REPL. I guess if you come from a compiled language
background, it’s pretty exciting, but my gateway drug to Clojure was Ruby, and
I’ve clocked up a lot of hours in
I immediately felt comfortable in the standard Clojure REPL just like IRB, and it’s fine for that, but I found Rebel Readline, with its ability to highlight, automatically pop up function arguments, and balance parentheses, made the experience much better.
REPL Integration and Editing
The REPL was great for getting started, and it’s quite feasible to put together complete programs in there, but when I learn a language I’m more comfortable writing something, running it, and iterating like that. This is where I hit a snag, because the JVM start up time makes it impractical to work like that.
A good Clojure work flow requires integration of REPL and editor. That is, an
IDE. I’ve tried various IDEs: I want to like them, I want to get it, but I
never get on with them. I want to use
vi, and proper
vi, not sketchy
bindings in something built not to use them. I use a Xerox Alto style portrait
mode screen with a pretty low resolution, and pretty big text (I’m old, okay?)
and modern IDEs are absolutely incompatible with that layout.
As I was picking up the language syntax, and writing 20-line programs, I quite
liked Nightcode, but I couldn’t use it for
anything non-trivial. I tried Atom, Lighttable, even Emacs, but whatever the
long-term benefits, twenty-five years of
hjkl habits are not easily
overcome. And learning Clojure was enough on its own, without having to learn
an IDE at the same time.
I also have vim-paredit, which takes care of bracket and quote balancing, and rainbow-parentheses makes the reading a little easier, particularly if you have a light-on-dark colourscheme. (Which I generally don’t.) It’s true what Lisp people say though: after a little while you don’t notice the parentheses.
To work on a Clojure project, I
cd to the directory and run
$ lein repl
then once it’s up, open a new terminal tab and
vi the file. I can evaluate
the expression under the cursor with
cpp, or run the whole program with
:%Eval. Output appears at the bottom of the screen. I’ve seen people do
fancier things with IDE REPL integration, but I’m happy with what I have.
I had the same problem with tests as with execution. When running
takes at least half a minute, the appeal of unit tests lessens dramatically.
Now I use lein-test-refresh,
a Leiningen plugin that re-runs tests whenever anything under
When I open the REPL tab I mentioned earlier, I also open a test tab, and run
$ lein test-refresh
Then I can ctrl-arrow between my full-screen editor window and the full-screen test output whenever I make a change. It’s a super-fast cycle. If I had more screen real-estate I would probably tile two windows together, but then I’d have to move my eyes, and I can’t be bothered with that.
I have looked at a couple of the other testing frameworks, but so far I like
clojure.test just fine, and I feel that if I have easy access to mocks and
stubs and spies, I’ll use them, rather than putting in the effort to write
more purely functional code which doesn’t need such things.
Linting and Static Analysis
I’m a big fan of static analysis, because it can teach you a lot about
idiomatic use of the language. I very much like
kibit, which integrates with
vim, and offers some excellent
advice. The same author also provides the linter
Eastwood and there’s a
vim plugin for that too.
Despite – or possibly because of – having worked in operations for twenty
years, deploying every kind of artefact on every kind of platform, I’m a big
It supports Clojure with virtually no effort, and works just great. Merge to a
release branch, and boom, it’s live. Lovely.
I’ve also deployed Clojure code into Amazon ECS using Docker. For minimum resistance, the images on Docker Hub work just fine (I favour the Alpine flavour), but it’s easy to start from a bare OS image and chuck in a JRE and Leiningen.
That’s my workflow. It’s simple and a bit old fashioned, which is probably why it suits me.