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Yearnote 2018

It’s time to look back at 2018 and talk about me.

On being a professional

The biggest thing for me personally was finishing my master’s thesis and graduating as a Master of Science. I’m glad it’s finally done. After graduating I continued working at Metosin as a software developer. In autumn, I joined Metosin’s board of directors.

At work, I took more responsibility on project management. It felt meaningful even if it always wasn’t fun. In general, I feel like I’ve made more mistakes lately. I reckon this is a good thing: either my job has become more challenging or I’ve become better at recognizing mistakes. Both mean more learning.

Here are some things I learned from, other than making mistakes:

On having a life outside work

These were fun:

Some cool cultural works:

What about my plans for 2019?

While 2018 was a pretty okay year for me, I know it was a hard year for a lot of people both on the personal and the societal level. Frankly, I’m not feeling optimistic about the politics. It will get worse before it gets better.

Finally, a year ago I wrote this:

I can’t believe it’s 2018 and Juha Sipilä’s cabinet still hasn’t fallen apart.

Unfortunately it’s 2019 and Sipilä’s cabinet still hasn’t fallen apart, but at least the parliamentary elections are coming up in April.


How I use tap>

A shadow against a bridge pillar on a rock.

One of the new features in Clojure 1.10 is tap. The changelog describes it as follows:

tap is a shared, globally accessible system for distributing a series of informational or diagnostic values to a set of (presumably effectful) handler functions. It can be used as a better debug prn, or for facilities like logging etc.

tap> sends a value to the set of taps. Taps can be added with add-tap and will be called with any value sent to tap>. The tap function may (briefly) block (e.g. for streams) and will never impede calls to tap>, but blocking indefinitely may cause tap values to be dropped. If no taps are registered, tap> discards. Remove taps with remove-tap.

I’m already using it as a better debug prn! I’m using Cursive and I connect to a REPL launched by Boot. With my setup, (prn :DEBUG value) has two potential downsides.

  1. The output may go either to the Boot terminal or to the Cursive IDE depending on the code path.
  2. The output is not pretty-printed.

Tap allows me to solve both problems. I want my debug prints to always appear in Cursive’s REPL, so after starting the REPL, I add a tap handler by running this command:1

(add-tap (bound-fn* puget.printer/cprint))

Here bound-fn* ensures that the output goes to Cursive and not to the terminal. Puget is the pretty-printer I’m used to, but you can replace it with your favorite printer. If you do not want to add new deps, you can use clojure.pprint or even plain old prn:

(add-tap (bound-fn* clojure.pprint/pprint))
(add-tap (bound-fn* prn))

Now when I want to debug-print something, I do (tap> "hello world"). Since both tap> and add-tap are in clojure.core, I don’t need to require anything. I can just tap> away.

Another debugging trick is to store the tapped value in an atom. I’ve used this only once so far, but it was pretty handy. Setup:

(def debug-a (atom nil))
(add-tap #(reset! debug-a %))

Now I can tap> an intermediate value in the middle of some complicated code and then poke at it in the REPL via @debug-a. Ideally you’d use a debugger, but if you are in hurry, maybe tap is enough.


  1. I don’t know how to do this automatically. If somebody knows, please tell me.


Clojure libraries I recommend

Brown maple leafs on the ground.

Every now and then I see people asking what Clojure and ClojureScript libraries they should be using. In this post, I’ll share my list of libraries for building full-stack Clojure/ClojureScript web applications. I’ve been building this kind of applications for a while now and I believe you can rely on these libraries.

Here’s what I’m looking for:

This list is not meant as the final truth: there are plenty of good libraries out there and you might choose different ones based on your needs and preferences. There’s an obvious bias, too: many of these libraries were made by my colleagues at Metosin.

Clojure backend

Framework. I appreciate the data-driven nature of Integrant. Combine it with Integrant-REPL for reloaded workflow.

JDBC database connection pool. I’ve never had any problems with HikariCP and it’s easy to configure and instrument. hikari-cp is a handy Clojure wrapper.

Configuration. I use Maailma and I’ve written about how to use it. cprop is very similar and probably a bit more powerful.

HTTP routing. I like the data-driven nature of reitit. It’s fast, too, and has enough extension points so that anything you want is possible. I would not use compojure-api because the implementation is way too hard to understand.

Logging. I use Timbre because it’s so easy to write custom appenders for it. Admittedly I haven’t checked out the popular Java options.

Test runner. Eftest is the test runner of my dreams and you can’t go wrong by using it. At some point I want to give Kaocha a go.

Test assertion library. I like testit and Juxt’s iota. They’re adequate, but I think there’s room to do better here.

Test data generation. I only just started using specmonstah for generating graphs of test data, but I’m excited. It’s so much nicer than writing the equivalent code by hand. There’s a bit of learning curve, though.

ClojureScript frontend

Build tool. Figwheel works very well and its getting better all the time. I’d either use it with Leiningen or directly with clj.

Front-end framework. re-frame is the way to go. Check out re-frame-10x for debugging.

Translations. Tempura works for me. I use a small Clojure tool for extracting the translatable strings into a PO file for editing with Poedit. The tool is proprietary right now but I hope to open source it.

General tools

clojure.spec helpers. Expound makes the spec error messages human-readable and Orchestra instruments the function return values.

Data manipulation utilities. I use the combination of Potpuri, xforms, and Specter. Potpuri is an old-fashioned “missing parts of clojure.core” library and xforms is the same for transducers. Specter is the closest thing to lenses for Clojure. It’s powerful but takes some time to learn. I recommend trying it out for some simple tasks – soon you’ll see opportunities for it everywhere.

What about …?

I haven’t included any SQL libraries, HTTP clients or servers, or async libraries, because I don’t have a clear recommendation for any of these (important!) categories.


For more posts, see archive.