Almost like Clojure

Practicing different programming languages has given me new insights in programming concepts, code styles and tools. My current crush is Clojure. I like the functional and data oriented style of it, the simplicity and minimalism. I think my favorite thing with Clojure, though, is how the REPL is used.

“What’s so cool about that repple thing?” 🧐

Testing at your fingertips 🚦

When using a code editor powered by a REPL, you can instantly evaluate variables, code blocks, functions or the entire file, just by a hitting a key combination. The result pops up right next to the cursor. This means that testing the code you currently write is at your fingertips. You are practicing a Deluxe version of Test Driven Development.

No copy-paste here 👮

It is not necessary to copy-paste code snippets into the actual REPL window or in a shell. In fact, you shouldn’t touch the REPL window at all. Because you don’t want to miss out on all the good stuff like autocomplete, hints and smart navigation that you have in your favorite editor.

For Clojurians only? 💭

I really would like to have a similar workflow in other languages too. It turns out there are some pretty good tools out there, the ones I’ve tried out so far are for JavaScript and ✨Emacs ✨.

Interactive JavaScript development 😍

Here’s me playing around with the node-zookeeper code. The cursor never leaves the editor window, the evaluation result is printed out in the Node.js REPL window to the right. More verbose than I’m used too in Clojure, but I think it works well.

Trying out code and ideas like this is a very nice workflow. I think you will find less need for debugging or console.log statements.

Keep on learning 📚

Learning a new programming language or tool can be really difficult, but also fun when the pieces finally start coming together. The knowledge gathered is something you can bring with you to other areas.

<sup>Have a look at my post about Emacs and my current configuration. The Node.js REPL feature is made possible using the js-comint package.

Photo by Marc-Olivier Jodoin on Unsplash</sup>

Simple (within parentheses)

• - Hey, what's ClojureScript?
• - It's a thing that compiles Clojure to JavaScript.
• - I get it. What's Clojure?
• - It's a Lisp.
• - ???
• - You know, a functional programming language that uses a lot of parentheses.
• - I … get it? 🤯

Don't worry. In this post, I will share some of the basics that I have learned about Clojure and ClojureScript.

Clojure?

With Clojure, you can write simple, functional and minimalistic code. Some of the cool things with Clojure are:

• data is immutable
• the REPL is a powerful tool
• few keystrokes to make things happen

Clojure runs on top of Java, suitable for all kinds of "backend" things. It also runs on top of JavaScript. Yes, JavaScript - making it possible to develop all kinds of apps, tools, products and websites. There's even an option to run in a .NET runtime, but I haven’t tried out that one yet.

What does it look like?

Even though the syntax may look unfamiliar, you can already see in this silly example the less amount of keystrokes needed using Clojure, compared to JavaScript.

Parenthesis?

Everything you write in Clojure is a list, wrapped in parentheses. That may sound weird. I agree, it is weird. But your eyes will get used to it. In short, the format of writing something in Clojure is:

(operator operands) or even (function arguments)

Here is an example:

... and how it would be written in JavaScript:

If all this is new to you, you might have this expression in your face right now: 😬

That is perfectly normal. I have looked like that a lot during 2020. When digging deeper, you may need to go through The 12 Stages of Learning Clojure.

ClojureScript?

With ClojureScript, you develop web apps and write simple React components. You write code in Clojure, compile it to native JavaScript and run it in your favorite browser. The compilation happens all the time and automagically as you type.

Just like with Java or .NET in the backend, ClojureScript has native access to JavaScript. You can use and interact with your favorite npm packages and React components just as you would with JavaScript.

Reagent and React

I'm going to fast-forward a bit by adding a ClojureScript library called Reagent. With Reagent, you write React components but with Hiccup instead of JSX. Wait, what?

View components are built up using Clojure data structures. The example above creates html elements with Clojure vectors and keywords. This style is called Hiccup. It will save you a lot of keystrokes and you'll have a lot less of scrolling in your code editor.

What about state?

I'll fast-forward again by adding a very nice library called re-frame.

From the re-frame docs:
“... It has reactivity, unidirectional data flow, pristinely pure functions, interceptors, coeffects, conveyor belts, algebraic effects, statechart-friendliness and claims an immaculate hammock conception. All while being both simple and easy. ...” 💥🤯💥

With re-frame, data is stored in one place called the "app db". Your components will fire events and subscribe to changes in the app db. The cool thing is that you write code in a sequential way, making it very readable and easy to understand. However, the syntax of the actual events and subscriptions might take a while to understand, at least if you are new to Clojure in general.

Here, we have a Reagent component that adds a button component, only when the app is disconnected. It is subscribing to changes of disconnected in the app db. React will re-render the components when the app state has changed.

Cool, but can I use my favorite editor?

Yes, most likely. I know there are Clojure plugins for VS Code, Atom, Sublime Text and intelliJ. I use Emacs, because ... I just like it.

There is something important and special going on with developers and their text editors. I think you will be able to find your favorite dev setup. I also think that you will learn a lot of new programming concepts and styles when reading more about this cool language and its libraries.

• Clojure
• ClojureScript
• Reagent
• re-frame

^{Photo by Marcos Paulo Prado on Unsplash}

The 12 stages of learning Clojure

In 2020, I've been on quite a learning journey. I joined a team where we write code in Clojure, a very different language from what I’m used to. It turns out writing Clojure is a very nice developer experience, but it could take a while to get it.

You might have to go through some (or all) of the 12 stages of learning Clojure.

😮
1. "I have no idea what I'm looking at."

😬
2. "Where does that code end? Where does it begin? Why are there so many parentheses?"

🤪
3. "I'm totally lost."

😳
4. "Will I ever learn? Am I smart enough?"

😭
5. "I will never learn. I'm not smart enough. I want ice cream!"

🤔
6. "Hmmm, wait a minute ... map, reduce, filter. This is something I recognize."

🙂
7. "Yes. Clojure, yes, yes."

🤯
8. "OMG, this language is so powerful. OMG, I even understand some of it."

🙃
9. "defn, keywords, multi-methods, macros, juxt, slurp, ha ha ha ha ..."

😀
10. "Pretty clean. Yeah, I've learned the keyboard shortcut to nicely format the code. And threading macros are nice!"

😍
11. "I ❤️ Clojure. Everything about it makes sense. It's is the language I've been searching for all my life."

🧘
12. "Empty your mind, be formless, shapeless - like water. Now you put water into a cup, it becomes the cup. You put water into a bottle, it becomes the bottle. You put it in a teapot, it becomes the teapot. Water can flow, or it can crash. Be water, my friend." *

You might wonder what stage I'm currently in. Well, probably somewhere between 🙂 and 😀.

Here's some of the sources that I have learned a lot from:

• Clojure for the brave and true
• Programming Clojure
• ClojureScript Koans
• Elements of Clojure
• Learn Reagent

I'm sure I will keep trying, failing, learning and mostly smiling in 2021 ✨

^{* Yes, Bruce Lee said that.}