(→ Stranded Between Parens)

The Lambda Island Blog

Fork This Conference

Last weekend Heart of Clojure took place in Leuven, Belgium. As one of the core organizers it was extremely gratifying to see this event come to life. We started with a vision of a particular type of event we wanted to create, and I feel like we delivered on all fronts.

For an impression of what it was like you can check out Malwine’s comic summary, or Manuel’s blog post.

It seems people had a good time, and a lot of people are already asking about the next edition. However we don’t intend to make this a yearly recurring conference. We might be back in two years, maybe with another Heart of Clojure, maybe with something else. We need to think about that.

But I do hope the legacy of Heart of Clojure can live on. One of the things we optimized for was socializing, making connections. We brought people from 31 (!) countries together, and enabled countless new connections. This will without a doubt have an impact on the Clojure community.

One of my goals with Heart of Clojure was also to provide people with new ideas. We had a very wide range of talks, many of them not directly related to Clojure, but all of them inspiring and sparking interesting conversation.

Finally I wanted to inspire other conference organizers. I have visited countless technical conferences over the years, and have developed strong opinions about what I think makes an event great. Some of these ideas are already wide spread, some of them are well accepted in other communities, but not yet prevalent in Clojure. In particular I was hoping to introduce some ideas from Ruby conferences like Eurucamp and Isle of Ruby into the Clojure community.

So that’s what this post is about, a quick recap of the specific things we did, that we would love to see others copy. Maybe the existing conferences will pick up a thing or two, or maybe someone else will feel inspired to create a new event. Seems there’s a market for a European summer conference, maybe you want to fill that gap?

A Two Phase CFP

This is already well known by now, but still worth mentioning. Our selection process occured in two steps. First we had a group of reviewers rate talks anonymously. They did not see the speaker’s name or other identifiable details, they just had the title and the abstract. This way you get a largely unbiased rating of the proposal itself.

Once all proposals are rated the program committee made a final selection. This time they did look at who the speakers were, to assure we had a balanced and diverse program, including first time speakers, and speakers from different places geographically, with a strong European representation, since we wanted to also showcase our local talent.

Finally also worth mentioning that after this final selection we paired all speakers up with a mentor. Some people worked together with their mentor extensively, others only checked in once or twice, but the offer was there, to make sure people are supported in delivering the best talk they could.

This is not the final word on finding a good CFP process, I heard that for ClojuTRE Metosin is experimenting with rating talks on multiple criteria, and then making a shotgun spread so you get talks across the spectrum. Hopefully they will write about their experience, and maybe even open source the app they developed for this.

To run our CFP we forked the CFP App developed for RubyConf.

Long breaks

We had 16 sessions spread over two days. That’s not that many, for comparison, the upcoming ClojuTRE has well over 20, which I’d say is fairly typical.

However we made the choice to keep the program fairly light. The sessions are what bring the people together, they provide inspiration and a shared experience, but in my mind a conference is really about meeting people, so we wanted to optimize for that.

We also wanted to prevent (to some extent) the mental exhaustion that easily sets in after a day of listening to talks. So we had plenty of breaks, typically half an hour each, with a one and a half hour lunch break the first day, and an extended lunch+siesta break on the second day.

This siesta break concept was pioneered by Eurucamp, and it took a little bit of convincing to get everyone on the team on board with it, but it’s so great, and people loved it. Basically on Saturday from noon to four people could do whatever. We offered lunch of course, and there were some activities to opt-in to (more on that later), but really it was “space intentionally left blank”. And so people grab a drink, sit on the grass, have long extended conversations. They go back to their hotel to freshen up or take a nap, they head into town, visit a museum, or pull out their laptops to share what they are working on.

The result: a much more interactive event, with deeper, more genuine connections. Trust me, four o’clock is there before you know it.

Activities

All these people travel to a country and city they’ve never been to, that has so much to offer, only to sit in a hall and stare at a screen until they’re exhausted. Isn’t that a shame? We wanted people to interact, to explore the city, to do things in small groups, which are so much more amenable to getting to know people.

So we organized Activities. We had guided city tours the day before, we did a creative code jam during the siesta break, there was a screen printing company on site where you could go to get our logo printed or create your own designs.

And other people could create activities as well. Juxt organized an impromptu workshop about Crux, people went bouldering, we had competing beer and wine tasting events, and over a dozen people learned from our sketchnoter Malwine how to sketchnote.

On Friday evening one of our speakers and Leuven native Maarten Truyens organized an “adventurous dinner”. Everyone who signed up got split into twelve groups of six to eight people each, and we made twelve different restaurant reservations, so people could get a dinner with a small group, and meet some of the other attendees, sponsors, and speakers.

Compare this with what usually happens: everyone stands around at the end of the day, clustering into ever bigger groups, and by the time you start moving you realize you need to on the spot find a place that will fit 20 people without prior notice.

To make this all possible we used the activities app first developed for Eurucamp, we just had to style it a bit, and promote it.

Lightning talks

This has always been one of my favorite parts of Ruby conferences. To qualify as a lightning talk a few requirements need to be met. The talks are exactly five minutes each, after five minutes the audience starts clapping and its over, and people sign up for them on the spot, by simply writing their name and talk title down on a big sheet that’s hung up in the venue.

If you like to have everything under control this may seem scary. There’s no telling what people will bring to the stage, but that’s what makes them so great. You get really spontaneous, diverse, and entertaining talks most of the time. And if it’s not, then in five minutes there’s already the next one.

This format allows people to show something they hacked together the day before, or to respond to a talk that they saw earlier at the conference. It allows people who feel a bit insecure to make a last minute call. It’s just a really great format, and I’ve rarely seen it gone wrong. Just make sure everyone is well aware of the code of conduct!

Also worth mentioning is that we did not end the day with lightning talks, which is fairly common. Instead we kept a closing keynote to close off the day and the event. This way you don’t end on the erratic, chaotic energy of the lightning talk session.

We also made sure this closing keynote wasn’t a deep technical talk. I’ve seen a few Clojure conferences do this, and I find it really hard to still engage with at the end of the day, my brain is just too fried. Instead we had a talk about community, focusing on the human aspects, which I thought was a great takeaway to end the day.

Start the second day a little later

Conferences bring far away friends together, and so what do they do after a day of focusing on talks? They go and relax, get a bite, grab a drink, and before you know it it’s two in the morning and you’re calculating how much sleep you can still get and if you’ll skip the first talk or not.

This isn’t necessarily what we recommend people to do, we did mention in a few places to be careful with Belgian beers, and to try and be fresh and bright in the morning (or to at least keep the partying until the end of the second day), but this is still the reality for a good part of the attendees.

So we start a little later the second day (and don’t start too soon in any case). The first day we had doors at 9:00, and started the sessions at 9:30, on Saturday doors opened at 9:45, and sessions started at 10:15. I’ve been to conferences where the first speaker on the second day is talking to just a handful of people, that’s not a fun place to be.

Conclusion

These weren’t the only things that made Heart of Clojure great, some things are harder to copy, and sometimes you have to get a little lucky. I think our biggest strength was the awesome venue, and we were lucky to find it, but it’s also our biggest weakness. If it had been a heat wave like the weak before, or if we had had serious thunderstorms, we would have been in trouble. We were also very close on capacity, there is no room to grow for us at this location.

We were also really lucky with the accessibility, being close to the train station and to Brussels airport, and to be in a city that’s compact and walkable. These are all circumstances that might be hard to replicate elsewhere.

And a final caveat: these things I listed here may not be the right thing for your event. You need to be the judge of that. Different people like different things, and different organizers set different priorities. But hopefully one or two of these ideas can trickle into some of the other great conferences we already have.

And if you do feel inspired to organize a new Clojure conference, once or repeating, then get in touch. We would be really happy to help. Maybe next summer?

More blog posts

Advice to My Younger Self

When I was 16 I was visited by a man who said he had come from the future. He had traveled twenty years back to 1999 to sit down with me and have a chat.

We talked for an hour or so, and in the end he gave me a few pieces of advice. I have lived by these and they have served me well, and now I dispense this advice to you.

Become allergic to The Churn

ClojureScript logging with goog.log

This post explores goog.log, and builds an idiomatic ClojureScript wrapper, with support for cljs-devtools, cross-platform logging (by being API-compatible with Pedestal Log), and logging in production.

This deep dive into GCL’s logging functionality was inspired by work done with Nextjournal, whose support greatly helped in putting this library together.

Clojure’s standard library isn’t as “batteries included” as, say, Python. This is because Clojure and ClojureScript are hosted languages. They rely on a host platform to provide the lower level runtime functionality, which also allows them to tap into the host language’s standard library and ecosystem. That’s your batteries right there.

The Art of Tree Shaping with Clojure Zippers

This is a talk I did for the “Den of Clojure” meetup in Denver, Colorado. Enjoy!

Captions (subtitles) are available, and you can find the transcript below, as well as slides over here.

For comments and discussion please refer to this post on r/Clojure.

Test Wars: A New Hope

Yesterday was the first day for me on a new job, thanks to Clojurists Together I will be able to dedicate the coming three months to improving Kaocha, a next generation test runner for Clojure.

A number of projects applied for grants this quarter, some much more established than Kaocha. Clojurists Together has been asking people through their surveys if it would be cool to also fund “speculative” projects, and it seems people agreed.

I am extremely grateful for this opportunity. I hope to demonstrate in the coming months that Kaocha holds a lot of potential, and to deliver some of that potential in the form of a tool people love to use.

Two Years of Lambda Island, A Healthy Pace and Things to Come

It’s been just over two years since Lambda Island first launched, and just like last year I’d like to give you all an update about what’s been happening, where we are, and where things are going.

To recap: the first year was rough. I’d been self-employed for nearly a decade, but I’d always done stable contracting work, which provided a steady stream of income, and made it easy for me to unplug at the end of the day.

Lambda Island was, as the Dutch expression goes, “a different pair of sleeves”. I really underestimated what switching to a one-man product business in a niche market would mean, and within months I was struggling with symptoms of burnout, so most of year one was characterised by trying to keep things going and stay afloat financially, while looking after myself and trying to get back to a good place, physically and mentally.

D3 and ClojureScript

This is a guest post by Joanne Cheng (twitter), a freelance software engineer and visualization consultant based in Denver, Colorado. She has taught workshops and spoken at conferences about visualizing data with D3. Turns out ClojureScript and D3 are a great fit, in this post she’ll show you how to create your own visualization using the power of D3 and the elegance of ClojureScript.

I use D3.js for drawing custom data visualizations. I love using the library, but I wanted to try one of the several compile to JavaScript options, and I decided to look into ClojureScript. It ended up working out well for me, so I’m going to show you how I created a D3.js visualization using ClojureScript!

What we’re visualizing

Reloading Woes

Setting the Stage

When doing client work I put a lot of emphasis on tooling and workflow. By coaching people on their workflow, and by making sure the tooling is there to support it, a team can become many times more effective and productive.

An important part of that is having a good story for code reloading. Real world projects tend to have many dependencies and a large amount of code, making them slow to boot up, so we want to avoid having to restart the process.

The Bare Minimum, or Making Mayonnaise with Clojure

Making Mayonnaise

Imagine you have a grandfather who’s great at making mayonnaise. He’s been making mayonnaise since before the war, and the result is truly excellent. What’s more, he does this with a good old fashioned whisk. He’s kept his right arm in shape throughout decades just by beating those eggs and oil and vinegar.

Now he’s bought himself a handheld electric mixer after hearing his friend rave about hers, but after a few tries he gives up and goes back to his whisk. He says he just can’t get the same result. This seems slightly odd, so the next time you go over you ask him to show you how he uses the mixer.

Clojure Gotchas: "contains?" and Associative Collections

When learning a programming language we rarely read the reference documentation front to back. Instead someone might follow some tutorials, and look at sample code, until they’re confident enough to start a little project for practice.

From that point on the learning process is largely “just in time”, looking up exactly the things you need to perform the task at hand. As this goes on you might start to recognize some patterns, some internal logic that allows you to “intuit” how one part of the language works, based on experience with another part.

Developing this “intuition” — understanding this internal logic — is key to using a language effectively, but occasionally our intuition will be off. Some things are simply not obvious, unless someone has explained them to us. In this post I will look at something that frequently trips people up, and attempt to explain the underlying reasoning.

Dates in Clojure: Making Sense of the Mess

Update 2018-11-27: while most of this article is still relevant, I no longer recommend using JodaTime as the main date/time representation for new projects. Even existing projects that aren’t too invested in JodaTime/clj-time should consider migrating to java.time and clojure.java-time across the board.

Update 2 2019-05-29: Also check out the talk Cross Platform DateTime Awesomeness by Henry Widd, given at Clojure/north 2019

You can always count on human culture to make programming messy. To find out if a person is a programmer just have them say “encodings” or “timezones” and watch their face.

Clojure Gotchas: Surrogate Pairs

tl;dr: both Java and JavaScript have trouble dealing with unicode characters from Supplementary Planes, like emoji 😱💣.

Today I started working on the next feature of lambdaisland/uri, URI normalization. I worked test-first, you’ll get to see how that went in the next Lambda Island episode.

One of the design goals for this library is to have 100% parity between Clojure and ClojureScript. Learn once, use anywhere. The code is all written in .cljc files, so it can be treated as either Clojure or ClojureScript. Only where necessary am I using a small amount of reader conditionals.

Simple and Happy; is Clojure dying, and what has Ruby got to do with it?

The past week or so a lot of discussion and introspection has been happening in the Clojure community. Eric Normand responded to my one year Lambda Island post with some reflections on the size and growth of the community.

And then Zack Maril lamented on Twitter: “I’m calling it, clojure’s dying more than it is growing”. This sparked a mega-thread, which was still raging four days later. A parallel discussion thread formed on Reddit. Someone asked if their were any Clojure failure stories. They were pointed at this talk from RubyConf 2016, which seemed to hit a lot of people right in the feels, and sparked a subthread with a life of its own.

Meanwhile Ray, one of the hosts of the defn podcast reacted to the original tweet: “I’m calling it: Clojure is alive and well with excellent defaults for productive and sustainable software development.” This sparked another big thread.

Loading Clojure Libraries Directly From Github

Did you ever fix a bug in an open source library, and then had to wait until the maintainer released an updated version?

It’s happened to me many times, the latest one being Toucan. I had run into a limitation, and found out that there was already an open ticket. It wasn’t a big change so I decided to dive in and address it. Just a little yak shave so I could get on with my life.

Now this pull request needs to be reviewed, and merged, and eventually be released to Clojars, but ain’t nobody got time for that stuff. No sir-ee.

Lambda Island Turns One, The Story of a Rocky Ride

One year ago to date I launched Lambda Island, a service that offers high quality video tutorials on web development with Clojure and ClojureScript. It’s been quite a ride. In this post I want to look back at the past year, provide some insight into how this experience has been for me, and give you a glimpse of what the future has in store.

This story really starts in December 2015. After three years of doing contract work for Ticketsolve I decided it was time for a change. I have been self-employed for many years, but I knew that sooner or later I wanted to try my hand at selling a product, rather than selling my time.

In January and February I took some time for soul-searching, and recharging. I went to speak at RubyConf Australia, and got to hang out with some old friends around Australia and New Zealand. Once back in Berlin I got busy creating Lambda Island.

Writing Node.js scripts with ClojureScript

In the two most recent  Lambda Island episodes I covered in-depth how to create command line utilities based on Lumo, how to combine them with third party libraries, and how to deploy them to npmjs.com.

However there’s a different way to create tools with ClojureScript and distribute them through NPM, without relying on Lumo. In this blog post I want to quickly demostrate how to do just that.

To recap, Lumo is a ClojureScript environment based on Node.js, using bootstrapped (self-hosted) ClojureScript. This means the ClojureScript compiler, which is written in Clojure and runs on the JVM, is used to compile itself to JavaScript. This way the JVM is no longer needed, all you need is a JavaScript runtime to compile and run ClojureScript code, which in this case is provided by Node.js. On top of that Lumo uses nexe, so Lumo can be distributed as a single compact and fast executable binary.

Announcing lambdaisland/uri 1.0.0

I just released lambdaisland/uri, a pure Clojure/ClojureScript URI library. It is available on Github and Clojars.

This is a small piece of the code base that powers lambdaisland.com. It’s inspired by Ruby’s Addressable::URI, the most solid URI implementation I’ve seen to date, although it only offers a small part of the functionality that library offers.

It’s written in pure Clojure/ClojureScript, with only minimal use of .cljc reader conditionals to smooth over differences in regular expression syntax, and differences in core protocols. It does not rely on any URI functionality offered by the host, such as java.net.URL, so it’s usable across all current and future Clojure implementations (Clojure, ClojureScript, ClojureCLR).

re-frame Subscriptions Got Even Better

Up until recently, to use re-frame subscriptions in Reagent views, you had to use a form-2 component.

A form-2 component is a function that returns another function, which does the actual rendering of the component to hiccup. In contrast, a form-1 component renders the hiccup directly.

;; form-1
(defn todo-item [todo]
  [:div.view
   [todo-checkbox (:id todo) (:completed todo)]
   [:label {:unselectable "on"} title]
   [:button.destroy {:on-click #(dispatch [:todos/remove (:id todo)])}]])

;; form-2
(defn todo-item [todo]
  (fn [todo]
    [:div.view
     [todo-checkbox (:id todo) (:completed todo)]
     [:label {:unselectable "on"} title]
     [:button.destroy {:on-click #(dispatch [:todos/remove (:id todo)])}]]))

Game Development with Clojure/ClojureScript

This weekend it’s Ludum Dare again, the world’s longest running game jam. The idea is that, alone or with a team, you build a game in a weekend based on a certain theme.

We got a little team together here in Berlin, and so I’ve been reviewing what options there are for someone wanting to build a game in Clojure or Clojurescript.

The good news is there are plenty of options, as you’ll see from the list below. You can do desktop games, browser based games with canvas or webgl, and you can even create Unity 3D games, all from your comfortable Clojure parentheses.

Union Types with Clojure.Spec

Elm and other statically typed languages have a great feature called Union Types (also called Sum Types or Algebraic Data Types).

Here’s an example taken from Elm. Suppose your system used to represent users as integers, maybe just an auto-incrementing primary key, but then switched to UUIDs represented as strings.

To correctly model this situation, you need a way to create a type that can be either an integer or a string, that’s what union types give you.