Clojure

🥷 Clojure Pro Tip 5: Hiccup Raw

Posted on 2025-05-15 (Last modified on 2025-05-17) | 1 minutes | 76 words

In case you don’t know it, we can use raw strings, like embedding JS code, in hiccup. I just found out we can use raw to prevent strings from getting escaped. I used to have to define a dedicated app.js for that, which would need an extra HTTP request. Hiccup raw in action Looking back, I should’ve found this at the very beginning, as it’s just mentioned on its GitHub homepage, but somehow I missed it. [Read More]

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🥷 Clojure Pro Tip 4: Cider ClojureDocs

Posted on 2025-04-29 (Last modified on 2025-05-17) | 1 minutes | 82 words

Sometimes, we may want a few examples of a Clojure API for inspiration while developing, especially when reading other people's or open source code. With Cider in Emacs, we can run M-x cider-doc to see the docstring for the symbol. We can even use M-x cider-clojuredocs for some examples if the symbol is from the language core. Running M-x cider-clojuredocs I happened to find this command recently. I bet I was not the only one who didn't know it, thus I'm sharing. [Read More]

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🥷 Clojure Pro Tip 3: the Thread-As Macro

Posted on 2025-04-23 (Last modified on 2025-05-17) | 1 minutes | 57 words

So you're more than excited to find out how Clojure's thread macros can make code clean and concise, you just love it! But at some point you'll be trapped a bit as the threaded argument's positions are inconsistent using -> or ->>.

Luckily, you can use as-> to place the argument wherever you like:

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🥷 Clojure Pro Tip 2: group-by

Posted on 2025-04-18 (Last modified on 2025-05-17) | 1 minutes | 47 words

It's amazingly easy to group things in Clojure. The language core provides a group-by function directly. Together with many built-in functions or key functions, it creates a ton of possibilities, and we can also bake our grouping function if none is satisfying.

Example from Clojure Koans.

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🥷 Clojure Pro Tip 1: the Discard Reader Symbol

Posted on 2025-04-05 (Last modified on 2025-05-17) | 1 minutes | 64 words

In Clojure, we can use comment (aka Rich Comment Blocks) for tests or experiments in development. However, since a comment evaluates to nil, you may run into surprising results or even errors if you misuse it.

In these scenarios, you may tend to use ; to comment them out, but a better choice is to use the discard reader symbol #_.

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Rewrite of a Flask Web App in Clojure

Posted on 2025-02-22 (Last modified on 2025-03-30) | 16 minutes | 3212 words

Intro A few years ago, I made a simple web app in Flask to deal with some text processing problems from my daily work. It has two main features: Feature #1: generating compile_commands.json for GNU Makefile projects written in C/C++ using the output of the make command. Because, unlike CMake, the make command can't generate it. Feature #2: extract text using Python regex. It's handy when I feel like sed/awk/grep's line-oriented processing isn't enough for the task at hand. [Read More]

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Constructing Clojure Maps Conditionally

Posted on 2025-01-05 (Last modified on 2025-02-20) | 1 minutes | 190 words

I was wondering how to construct a multi-key map conditionally while I was coding in Clojure. Ideally, I would like to build it "in one pass" like {:bar 2 (when true :baz 3)}, but from what I had collected from Blue Sky, it seemed that's impossible, or it's just not an idiomatic way to program like that in Clojure. (Or, is this just a side effect of writing too much imperative code? [Read More]

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Getting Started with Cider for Clojure Programming

Posted on 2024-12-22 | 2 minutes | 303 words

Here is the outline for my cider tutorial on YouTube, covering basic things you need to know to get started with cider, and starting exploring the fun of clojure programming with the REPL-driven programming approach. Jack In to a REPL C-c M-j (cider-jack-in-clj) start a nREPL and jack in. It works in a project or with a sole .clj file. M-x cider-connect-clj run the command and then fill in hostname and port. [Read More]

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A Few Quick Notes About babashka/fs

Posted on 2024-12-07 (Last modified on 2024-12-19) | 1 minutes | 149 words

Recently I've used babashka/fs a little bit, here are some quick notes for it: Path vs File. Use Path whenever possible, according to this SO answer to "Java: Path vs File". This is actually Java related. It's ok to use a path as a key for a clojure map. At my first try, I somehow came to the conclusion that it's not ok, while I was refactoring the live reload for clay. [Read More]

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Doing Unit test in Clojure Is Easy

Posted on 2024-11-28 (Last modified on 2025-02-26) | 1 minutes | 165 words

While refactoring the live reload feature of Clay, I realized I'd better break long functions into smaller and functional ones (as many as I can), which is also a common practice in the clojure community. Small pure functions not only are easy to verify on the development process (using a REPL), but also are easy to test. And unit tests are easy to write in clojure, just use deftest from clojure. [Read More]

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