UPDATE: 2017-05-12 A few more thoughts have come to mind after writing the original post. I realized that I didn’t talk about the clojurescript side of things. Clojurescript provides a great alternative to plain javascript or ES6. The thing about clojurescript is clojurescript has the clojure standard library, which includes many more functions than javascript. The left-pad incident made me realize how weak a standard library javascript has. People need to write so many tiny libraries in order to get functionality that would exist in other languages. Read more...

People coming from opinionated frameworks like Ruby on Rails often become disoriented in a Clojure project. Rails, being a framework, has the code already organized for you. You just had to learn where to put your models, views, and controllers. Clojure doesn’t have a major opinionated framework like Ruby on Rails that forces you to follow its conventions. A lot of beginners get confused and have questions like the following: Read more...

Here’s the sitch: You want to learn Clojure. You don’t know which editor to use. You do research and it looks like everybody is saying emacs is required to edit Clojure. You’re wondering what your options are and if you’ll be missing out if you’re not on emacs. The problem with the many Clojure resources out in the wild is that they’re outdated. They suggest that Emacs is the only way to go when editing Clojure, which leads to you being frustrated as a non-Emacs user. Read more...

We’ve all been there. You’re hacking away on some Clojure code, making a few changes and then try to run the code in your REPL. Instead of getting the result you wanted and your tests passing, you get your worst nightmare: UnsupportedOperationException nth not supported on this type: IPersistentMap And the first thoughts that pop into your mind are: I’m not calling nth anywhere! What the hell? Then you google ‘nth not supported on this type: IPersistentMap’ and don’t get anything particularly useful and you proceed to bisect your code manually to find the problem. Read more...

I’ve been getting questions from beginner Clojure developers on how to effectively use their REPL and interactive development. Quite a few of these people are coming from languages like Java, where they would have to compile their application and wait before running any code. Integrate your REPL with your editor You must have your REPL integrated with your editor. Whether that’s a text editor like emacs with cider, or an IDE like IntelliJ with Cursive, you have to be able to evaluate code in your REPL from the editor. Read more...

HN Comments 2021: https://news.ycombinator.com/item?id=28577371 Last year, I submitted a PR to the Clojure web request routing library, Compojure. Even though I was doing Clojure full time at work, there was still a lot for me to learn and always will be. Opening a PR for an open source library I was familiar with and used all the time made me realize a few things: I didn’t know it as intimately as I thought I did. Read more...

Checking For An Empty List Don’t use (not (empty? coll)). Instead prefer (seq coll) instead. Seq returns nil if the collection is empty. If the seq isn’t empty then it returns a seq on that collection. Flattening The Result Of A Map By One Level If the result of a map function ever returns a list of lists, then use mapcat over (apply (concat (map...))): (map list (range 10)) ;; => ((0) (1) (2) (3) (4) (5) (6) (7) (8) (9)) (mapcat list (range 10)) ;; => (0 1 2 3 4 5 6 7 8 9) Maps Are Functions Maps, like keywords, are functions. Read more...

A lot of people have already heard that they should use Stuart Sierra’s component library to manage state in their Clojure applications. But most don’t know why and how you would incorporate it into your software. This how to guide will give you all the tools you need to start managing state in your Clojure software. What is component? Component is a Clojure library that can be thought of as a micro dependency injection framework. Read more...

Backstory I wrote an article on how I decided to go with Ruby instead of Clojure a while back. I moved my blog from Wordpress to Jekyll yesterday and think it’s time for an honest update. I also have a Node.js and Clojure comparison article if you’re also interested. It tells a different side of a similar story for people looking to pick between Javascript and Clojure. Performance and Speed Clojure and Ruby is often an order of a magnitude faster than Ruby for compute based tasks. Read more...

When developing applications in Clojure, one thing you might need is to be able to somehow keep different settings for each environment. For instance, you might want to be able to have different database settings for each environment. This can be achieved with leiningen profiles: ```clojure :profiles {:dev-overrides {} :dev [:dev-overrides {:dependencies [[com.cemerick/austin "0.1.5"] [com.cemerick/piggieback "0.1.4-SNAPSHOT"] [ring-mock "0.1.5"]] :plugins [[com.keminglabs/cljx "0.5.0"] [com.cemerick/austin "0.1.5"] [lein-cljsbuild "1.0.3"]]}] :test-overrides {} :test [:dev :test-overrides]} ``` Assuming you have that :profiles sub-map somewhere in your project. Read more...