Ken Huang

Your Screenshots Deserve Better. Introducing Backdrop.

Tue, 10 Mar 2026 22:49:27 +0800

Have you ever been there? You've just finished a brilliant piece of code, designed a slick UI, or found the perfect example for a tutorial. You take a screenshot to share your work, but when you look at it… it's just… plain.

You could share it as is, but it lacks professionalism. Or, you could spend the next 15 minutes wrestling with a heavy-duty design tool, carefully placing it on a background, adding a shadow, and rounding the corners, all for a single image.

🥷 Clojure Pro Tip 5: Hiccup Raw

Thu, 15 May 2025 12:49:27 +0800

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.

🥷 Clojure Pro Tip 4: Cider ClojureDocs

Tue, 29 Apr 2025 12:49:27 +0800

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.

🥷 Clojure Pro Tip 3: the Thread-As Macro

Wed, 23 Apr 2025 12:49:27 +0800

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:

Lambda vs. thread-as

🥷 Clojure Pro Tip 2: group-by

Fri, 18 Apr 2025 12:49:27 +0800

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.

group-by

Example from Clojure Koans.

Collecting Events to Google Analytics using ClojureScript

Fri, 11 Apr 2025 22:49:27 +0800

When you’re building a side project, chances are you need to collect user events so that you can understand user behaviors better and eventually improve your product.

So recently I made a small ClojureScript library for that, it supports web apps or chrome extensions. Check it out at https://github.com/whatacold/google-analytics, it also contains a demo project using shadow-cljs as the build tool.

Hope it helps, and give it a star ⭐ on GitHub and share it if it does, thanks!

🥷 Clojure Pro Tip 1: the Discard Reader Symbol

Sat, 05 Apr 2025 12:49:27 +0800

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.

Comment vs. Discard

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

Rewrite of a Flask Web App in Clojure

Sat, 22 Feb 2025 22:46:05 +0800

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.

BTW, I'm improving my English by watching YouTube videos every single day; If you're also learning English, or any languages, LanguagePuppy can definitely help you. It's a Chrome extension I developed using Clojure. Check it out:

Constructing Clojure Maps Conditionally

Sun, 05 Jan 2025 10:40:07 +0800

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?)

Getting Started with Cider for Clojure Programming

Sun, 22 Dec 2024 17:17:15 +0800

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. It could be useful in some cases. e.g. on Windows, I can start the nREPL manually and then connect to it separately.

Evaluate Things

C-M-x (cider-eval-defun-at-point): evaluate current top-level form.
C-x C-e (cider-eval-last-sexp): evaluate the preceding form.
C-c C-k (cider-load-buffer): evaluate/load the current buffer.
C-c C-p (cider-pprint-eval-last-sexp): Pprint the result in a dedicated buffer. Great thing to do when the result is too large to fit in the echo area.

Note: I prefer to use the same key bindings as for Elisp, given that cider might bind a few keys to a single command!

A Few Quick Notes About babashka/fs

Sat, 07 Dec 2024 22:24:41 +0800

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. And later I found that it's totally fine to use it as a key. 😞
Use fs/path to construct file/directory paths, for example, (fs/path "/tmp" "foo" "bar" "baz.clj") will result in a path object for /tmp/foo/bar/baz.clj on linux. If you're coming from Python, it might remind you of os.path.join(path, *paths).
Use fs/createdirs for mkdir -p, though its name is a bit misleading, I first thought it's for creating a few dirs.
fs/with-temp-dir is convenient for creating tests.

Doing Unit test in Clojure Is Easy

Thu, 28 Nov 2024 23:10:56 +0800

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.test, a very basic one looks like this:

Clj-async-profiler Rocks

Thu, 28 Nov 2024 22:23:32 +0800

While developing the live reload feature for Clay, a minimalistic Clojure tool for data visualization and literate programming, I found that it constantly takes ~1 minute for beholder to watch a directory. After some code inspect, I was still having no idea why it happened.

So I decided to use a profiler to find out what's going one under the hood, and Google immediately took me to clj-async-profiler. It's easy to set up following its basic usage docs:

TailwindCSS Docs Index

Sat, 23 Nov 2024 19:50:56 +0800

Just re-organize the TailwindCSS Docs index in a flatter and more searchable way.

Getting Started

Core Concepts

Customization

Base Styles

Preflight

Layout

Adding Clojure Dependencies from the Command Line

Sat, 09 Nov 2024 21:02:56 +0800

While debugging a live reload issue of Clay a few days ago, I learned from Markus Agwin that we can actually add dependencies on the fly from the command line, just like this: clj -Sdeps "{:deps {org.scicloj/clay {:mvn/version \"2-beta21\"}}}".

Even better, we can add dependency from a Git repo and specify the commit hash: clj -Sdeps "{:deps {io.github.scicloj/clay {:git/url \"https://github.com/scicloj/clay.git\" :git/sha \"35a46541db66ae6b4e1af628b7c24c42d3be418f\"}}}", which is really helpful for experimenting and verifying things.

Some clj links (clj --help has a pointer for these URLs):

Bitten by Lazy Sequence of map

Sat, 09 Nov 2024 21:02:56 +0800

While impletenting the live reload feature for Clay a few weeks ago, unfortunately, I was bitten by the laziness of map. It seems quite obvious we all know that its result is a lazy sequence, but I just can't help fall into the "trap".

At that time I was adding a vector to keep track of all beholder instances watching file changes in user specified directories. So then when it's time to stop all the watchers, I used something like to achieve the goal:

Anonymous Functions in Thread Macros

Fri, 08 Nov 2024 21:02:56 +0800

While adding the live reload feature to Clay, I encountered a problem of applying anonymous functions to thread macros. For example, below is a simple snippet trying to wrap the input directory as a vector with the help of thread macro, but surprisingly, it errors out. After some searching, I figured out that I need to put the anonymous function into another pair of parentheses:

(-> "/tmp/"
    #(if (vector? %) % [%]))
;; => Syntax error (ClassCastException) compiling fn* at (simple4all.clj:19:1).
;;    class java.lang.String cannot be cast to class clojure.lang.ISeq (java.lang.String is in module java.base of loader 'bootstrap'; clojure.lang.ISeq is in unnamed module of loader 'app')

(-> "/tmp/"
    (#(if (vector? %) % [%])))
;; => ["/tmp/"]

Paul has a nice explanation on Stack Overflow, thread macros need the function forms to be lists, but anonymous functions are already lists, so the first expression, "/tmp/" in this example, will just be inserted into that list, just as illustrated below:

Starting a Clojure nREPL Manually for Cider

Fri, 08 Nov 2024 00:02:56 +0800

While troubleshooting and fixing a live reload bug in Clay today, which required to start a minimal Clojure environment, I figured out how to start a nREPL from the command line.

Instead of using M-x cider-jack-in-clj directly from Emacs, actually we can manully bring up an nREPL with this: clj -Sdeps "{:deps {org.scicloj/clay {:mvn/version \"2-beta21\"} cider/cider-nrepl {:mvn/version \"0.50.2\"}}}" -m nrepl.cmdline --middleware "[cider.nrepl/cider-middleware]" (The clay part is only necessary for this debugging), and then connect to this nREPL using the Emacs command M-x cider-connect-clj.

Join Every N Lines By A Separator in Emacs

Sat, 25 Nov 2023 12:24:24 +0800

It has been some time since I came along the idea of the w/join-lines command to join lines. After that, sometimes I found that it would be even better to join every a few lines.

Let's see the example below, suppose we've copies some data from somewhere, and now we want to yank it into an Emacs buffer and slightly modify it to be like an matrix.

That is, make it from:

Restoring Emacs' Window Layouts

Sun, 19 Nov 2023 13:02:42 +0800

If you've been using Emacs for a while, I bet you must have encountered the annoying problem that your Emacs window layout gets messed up after some operations, such as looking for a help (e.g. C-h k), or checking things in the magit status buffer.

Photo by R Mo on Unsplash

I'm happy if I can just get back to the previous layout that I had before, and guess what? Emacs happens to have that capability built in – the winner-mode package, what a surprise!

Emphasize Text By Dragging Mouse in Org-mode

Mon, 14 Aug 2023 22:48:20 +0800

Long story short, I came up with an idea to emphasize content while I was reviewing an org-mode document a few months ago after I was tired of typing tedious * around the content repeatedly. And I've been longing for this feature since then, because I was unfamiliar with mouse-based key bindings, and neither did I have the time to investigate it.

Today I finally nailed it down while I was attending a boring meeting, and it turned out to be quite simple. The exploration journey was not much different than before. First, I managed to find out how to bind a command to a mouse event, taking advantage of the good-old C-h k and (info "emacs") (or here at gnu.org). And then wrote a few lines of code to perform the task standing on the shoulder of Advice.

Join Lines By A Separator in Emacs

Mon, 12 Jun 2023 22:23:12 +0800

So sometimes I need to join a few lines by a separator while I'm coding, for example, turn the below lines,

foo
bar
baz

into foo + bar + baz. (This is a silly example, I will update if I come up with a better one :-P )

When I was in a rush in the past, I usually baked a keyboard macro temporarily and then applied it to achieve this goal, thought reliable, it's a little bit cumbersome to record it. So I wonder maybe it would be a good idea to have a command for it.

Hugo Blogging in Emacs

Mon, 10 Oct 2022 22:50:48 +0800

When I started to use Hugo to write this blog last year, I noticed that there is an easy-hugo package of Emacs many people use. So I installed it at that time, but I didn't use many of its features since then. In fact, the only command I used was easy-hugo-current-time. I used it to update the Hugo timestamps manually as in the format of 2022-10-15T09:45:35+08:00.

My most desirable feature is to use it to select tags easily when I start to write a new post, but I never got it to work.

Auto-complete Accounts From Other Beancount Files in Emacs

Sat, 10 Sep 2022 11:13:38 +0800

Auto-complete accounts from another accounts.bean file

If you're using Beancount with Emacs, you may be using beancount-mode. It can auto-complete the accounts defined in the current buffer when we are typing in new transactions so that we can do it more efficiently.

But it can only auto-complete the accounts from the current buffer, which makes it less useful when we have a stand-alone file or a few files of beancount accounts.

A Bookmarklet for Copying a Link as an Org-mode Link

Mon, 08 Aug 2022 23:33:05 +0800

In this blog post, I'd like to share a bookmarklet for copying a web page's URL as an org-mode link on Firefox, Chrome, or whatever web browsers support bookmarklets.

It's handy when the URL isn't SEO-friendly, which means you can't tell what its content is about at first glance of the URL. So a little description text on the link would help.

Here is the bookmarklet:

javascript:window.prompt("Copy to clipboard: Ctrl+C, Esc", "[[" + document.location.href + "][" + document.title + " - " + document.location.hostname + "]]");

// Don't know why the page becomes blank after using it on Firefox, so use alert instead.
javascript:alert("[[" + document.location.href + "][" + document.title + " - " + document.location.hostname + "]]");

Add a new bookmark on the browser, give it a name, such as (org-link), and then copy and paste the content as URL, just like below on Firefox:

Emacs Debugging Techniques

Sun, 17 Jul 2022 09:57:31 +0800

If you are new to Emacs, you may run into some errors, especially after you copied some elisp snippets from the Internet or elsewhere. Don't panic! It happens, it's just part of the learning process. Even an experienced Emacs user could run into there issues from time to time.

Duplicate the current line in Emacs

Mon, 23 May 2022 21:29:28 +0800

Duplicate the current in Emacs

Duplicating the current line is frequent editing for me when I am coding. Initially, I copied a snippet as a command in Emacs from the Internet:

(defun w/duplicate-line()
  "Duplicate the current line."
  (interactive)
  (move-beginning-of-line 1)
  (kill-line)
  (yank)
  (open-line 1)
  (next-line 1)
  (yank))

Most of the time, I was happy with it, but it has mainly two drawbacks:

It cannot keep the column position when moving to the next line
It messes up with the yank ring as it yanks the text under the hood

So today, I took some time to fix these two problems, and I also want it to be capable of commenting the current line out if I prefix the command.

Adjust the laptop's screen brightness in Emacs

Sat, 21 May 2022 11:50:25 +0800

Adjust the screen brightness in Emacs

If you're using i3wm on Linux, how do you adjust the laptop's screen brightness?

Most of the time, I use the laptop with an external monitor. But when I am out, I have no monitors. And it seems no easy way to adjust the brightness in i3wm. Being too bright or dim is terrible for the eyes.

How to Kill a "Visible" Buffer Quickly in Emacs

Sat, 09 Apr 2022 23:11:36 +0800

Selecting Emacs windows using ace-window

Recently I've been building a simple Emacs config for myself, along the way I re-discovered some fantastic packages, for example, I found that ace-window is a simple yet powerful package to enhance the default other-window command to select other windows quickly when it has more than two windows in a frame.

I replaced the key binding of other-window to ace-window by simply doing (global-set-key (kbd "C-x o") #'ace-window), then when there are >2 windows, it will show a white-in-red number at the top-left corner for every window, hit the number (1, 2, 3, …) and then Emacs will select the corresponding window (as demonstrated in the above screenshot).

How to append items to the CSV file without header row?

Sat, 09 Apr 2022 22:32:11 +0800

Scrapy Architecture

Scrapy provides a few item exporters by default to export items in commonly used file formats like CSV/JSON/XML. I usually use CSV to export items, it is pretty convenient, and it comes in two ways:

appending mode, for example, scrapy crawl foo -o test.csv
overwriting mode with -O option, like scrapy crawl foo -O test.csv

But in the appending mode, it's a bit annoying that it always appends the header row before the newly scraped items, which is not correctly in terms of CSV format.

About Me

Wed, 09 Mar 2022 12:37:20 +0800

Hey, welcome to my blog site!

This is Ken, who is passionate about technology and a lifelong learner. Here I share my experiments and thinking on technology, especially Clojure/ClojureScript and Emacs stuff. Bookmark this site or follow me on social media, the links are at the bottom.

Besides, I also make and post videos to my YouTube channel from time to time, please subscribe if you're interested!❤️

Interesting OSS Projects I Contributed

Clay is a note-taking and data visualization software written in Clojure, and it's REPL friendly.
org-anki is an Emacs package helping you sync notes in org-mode to Anki, and learn better in general.
Qtile is a full-featured, hackable tiling window manager written and configured in Python.
Doxygen is the de facto standard tool for generating documentation from annotated C++ sources.

Interesting Personal Projects

(I use these tools from day to day, both at work and in daily life, so it's truly "For Developers, By Developers"!)

Eglot for Better Programming Experience in Emacs

Sat, 22 Jan 2022 11:36:18 +0800

LSP, or Language Server Protocol, makes programming easier by introducing features like more precise auto-completion and definition lookup. It may have scratched your itches, and you may wonder what the experience is like in Emacs.

How to Reload i3status config On the Fly

Fri, 14 Jan 2022 22:36:13 +0800

Sometimes I want to change the status (i3status) of i3wm temporarily, but it seems that i3wm doesn't support it directly, although reloading the config for i3wm itself is a piece of cake (bindsym $mod+Shift+c reload in the config, or i3-msg -t command reload in the command line).

But this issue scratched my itch, and I swear that I must solve it today.

Language Shadowing with subed in Emacs

Wed, 12 Jan 2022 21:41:54 +0800

So I'm trying to improve my English speaking skill by shadowing while watching TV episodes. The workflow before was to loop over video clips using mpv:

hit l to mark the start of the loop
play the video and wait for it to be at the end of the loop
hit l again to mark the end

Then mpv will loop over the clip, it basically works, but it's a bit hard and tedious to set the start and end precisely.

Writing a Python Script in Emacs in 45 Minutes!

Sat, 11 Dec 2021 09:24:53 +0800

Note: watch my live coding session of this article:

Intro

If you've heard some rumors of Emacs that it has a very steep learning curve (or that Emacs makes a computer slow), you may be too scared to look at it. It indeed has some learning curve (learning anything does have one), but it isn't very steep. I learned this after getting my hands dirty with Emacs a few years ago.

Beautiful Soup 4 Cheatsheet

Sat, 25 Sep 2021 23:01:40 +0800

Beautiful Soup

Detailed docs: the Beautiful Soup 4 Docs.

Assume t is an object of Tag.

Core concepts (classes)

Tag, a Tag object corresponds to an XML or HTML tag.
BeautifulSoup, the BeautifulSoup object represents the parsed document as a whole. You can treat it like a special Tag. It needs a parser to parse the document, a built-in parser is "html.parser", e.g. soup = BeautifulSoup("<html>a web page</html>", 'html.parser')
NavigableString, a string corresponds to a bit of text (as you see it in the browser) within a tag. A NavigableString is just like a Python Unicode string, except that it also supports some of the features for navigating the tree and searching the tree.

The `Tag` class

Object attributes:

Clojure reduce: one case for text processing

Sun, 19 Sep 2021 10:39:23 +0800

As a practice, I managed to illustrate Clojure files using illustrate.clj, but my original idea was to annotate org-mode files of blogs. It's not uncommon that a blog post has some code snippets.

But it missed the feature until last night, as I wasn't sure how to implement it appropriately before and didn't have enough time.

For example, I may have an org-mode like this:

sum of two numbers:
#+begin_src clojure
(+ 1 2)
#+end_src

I want to have a result comment ((;; => 3)) after each top-level form after using illustrate.clj: sum of two numbers:

illustrate.clj to Illustrate Clojure Snippet

Sat, 07 Aug 2021 18:49:25 +0800

To get my hands dirty with Clojure, I am trying to find or implement Clojure's string functions in the sense of Python. Python has powerful string APIs, and I also want to see how powerful Clojure could be in this field. That would be interesting.

As shown in the cheatsheet, Clojure has implemented most of them, and there are some that I have to implement myself, like title-case.

Along the way, I found it was a little cumbersome to append the evaluation result and the result of calling them, for example,

String Title Case in Clojure

Sun, 25 Jul 2021 11:51:39 +0800

These days I like to write scripts for some tasks in Python instead of shell. One important reason I think that's because Python is powerful at string manipulation.

Recently I'm learning Clojure, and I'm trying to find similar ways in Clojure, one of them is s.title() for getting a title-cased version of a string. For example,

>>> ' Hello world'.title()
' Hello World'

How to do that in Clojure? To make the problem simple, let's assume that the input string only has letters and spaces, that is, [a-zA-Z ] in regex pattern.

String Manipulation in Clojure

Thu, 22 Jul 2021 23:29:11 +0800

Python string APIs are powerful and concise, that is an important reason I use it to do a lot of scripting these days, join, split, strip, to name a few.

Since I am learning Clojure recently, I am wondering, how is string manipulation like in Clojure and how to implement equivalent ones?

I think it's an excellent opportunity to get familiar with Clojure. Before diving into the implementation, how to declare a multi-line string?

Send Notifications from Emacs with i3wm and Dunst

Sat, 17 Jul 2021 12:22:10 +0800

I barely use notifications, but recently I think it's a valuable way to remind me things like helping me nurture habits, or to notify me of emergencies like a critically low laptop battery.

So I try to integrate notifications to org-mode and Emacs today.

The org-notify package from org-contrib (install it by (package-install 'org-contrib) ) could do this job easily before, so I first test it in the minibuffer with (org-notify "test").

Unfortunately, it errors out:

A Random Password Generator in Babashka

Sun, 11 Jul 2021 09:18:41 +0800

I'm used to learning by practicing, so when I learned Clojure, I always kept an eye on chances to write code in it.

Scripting is an excellent field to practice, but the experience is not so good. On the one hand, it's too hacky to wrap Clojure code in a shell script with the shell bang. On the other hand, the startup time of JVM is too long to hurt the user experience.

An Online Python re.findall Service

Wed, 21 Oct 2020 22:51:00 +0800

As a programmer, I know that grep, sed and awk are powerful for processing text, but they sometimes aren't that straight-forward for specific tasks, as I need to think about how to filter the lines and the columns out.

So I wonder if there is a handy way to do these tasks?

After using it for a while, I think using regex directly can help, so I launched a re.findall service building on top of Python re.findall API.

Generate Call Graphs Using Doxygen in Emacs

Sat, 22 Aug 2020 18:57:00 +0800

Doxygen is a nice tool for generating documentations for well-annotated C/C++ projects, the one feature that I like most is generating call graphs and class diagrams, so that I can learn a project quickly by browsing the diagrams from a higher point of view.

I take the following steps to generate call graphs for a project on terminals on Linux:

cd /path/to/a/project/, and generate a template config file by doxygen -s -g doxygen.conf (Omit -s to generate it with detailed comments).
Tweak the file by specifying input and output directories, and set HAVE_DOT and CALL_GRAPH to YES.

Is It Safe to Use Redis As a Data Store?

Thu, 25 Jun 2020 22:37:00 +0800

Traditionally we are used to storing data in an RDBMS like MySQL, and avoid using in-memory solutions such as Redis, to have a confidence of no data loss. Sometimes I find that we are so stubborn with MySQL that ending up with a complicated design, and I've even seen a solution that stores data in MySQL and then using Redis as a cache for it to improve read performance in the meanwhile. And to make the data in the cache as consistent as possible with the data in MySQL, it introduces other mechanisms, but the result is still not 100% consistent.

A Trick to Troubleshoot Emacs Subprocess Creating

Sat, 30 May 2020 11:52:00 +0800

There are many packages of Emacs that leverage subprocesses to do their jobs, Magit, eglot, elpy, to name a few. And there are times that a subprocess doesn't work as expected, for example, Magit is slow, and you're sure that it's ok when running git commands on shell. So how to spot these problems effectively and quickly?

The problem is that we don't know what's going on exactly, so here I want to share a few Elisp advices to make the subprocess creating visible, and print the exact program and its arguments to the *Message* buffer. Visibility is the key.

ppcompile: An Emacs Package to Help Coding Locally

Sat, 07 Mar 2020 23:50:00 +0800

If you are a C/C++ programmer like me, you may experience jumping around different machines to write and compile your code, or you may write code on different machines for different projects, and scp/rsync/ftp the projects around. It works, but it's a bit tedious and takes too much burden on our brains.

For example, say I have two projects that should be compiled on their compiling machines respectively. There are two obvious workflows for writing code for them "simultaneously":

The Binary Search Idea for Narrowing Down Problem Space

Tue, 04 Feb 2020 18:48:00 +0800

Binary search algorithm is a search algorithm that finds the position of a target value within a sorted array. It cuts off the target array in half in a pass, so that it has a worst-case performance of O(log n).

Visualization of the binary search algorithm where 7 is the target value(@wikipedia)

We all know that it's an efficient searching algorithm, but the strategy behind it also applies for narrowing down other problem space, for example, finding out when a bug is first introduced in a series of git commits.

Manage SSH Connections with ~/.ssh/config

Sun, 22 Dec 2019 18:52:00 +0800

I used to manage SSH connection with such GUI apps as MobaXterm, when I wrote code on Windows at work. As I changed my workflow to use a tiling window manager in a VirtualBox guest OS, I continued to improve my way of managing SSH connections, which I want to share here if you don't know yet.

At first, I baked a helper Python script, which I named as qssh for "quick ssh", to help me assemble ssh arguments for me(such as username, Ip, port, etc.), so that I can easily access a host by giving it only one argument, e.g. qssh foo.

Why Can't Git Fetch Remote Branches Other Than Master?

Sun, 01 Dec 2019 16:00:00 +0800

Last week I came into a problem with Git, that I can't fetch the remote branch that I just pushed to. It was so weird because I can push it. It never happens before, and it happened when I was in a rush to rebase my code, as someone in my team pushed his code.

After searching, it seemed that the configuration of fetch of that repo was different(this Stack Overflow thread for example) than before, it was specified that only master can be fetched. It worked after I changed it to +refs/heads/*:refs/remotes/origin/*.

Open New Urxvt from within Emacs

Mon, 25 Nov 2019 22:47:00 +0800

I have been really enjoying the more concentration workflow qtile, a tiling window manager, brings me, since I started using it a few months ago. I am more focus on the current task now as all the windows I care about are laid out on the same screen.

As I get more used to qtile at every day's work, I noticed that I became more depend on short-life terminal sessions. Sometimes I need to quickly execute some commands on the current buffer on Emacs, such as searching text which having many matches and quit that terminal after I'm done. So I wondered what could be the best way to achieve that.

Build Docker Images for Qtile

Mon, 07 Oct 2019 13:25:00 +0800

One of Docker's use cases is to set up identical development environments easily and quickly for a dev team. Recently, I had an opportunity to give it a try, and build Docker images for Qtile, as it didn't have one yet as I get involved. With the images, it's easy to set up the environment to easily run the tests, and build the documentation.

The best way to have a basic idea of Docker is to think it like a chroot environment, as Chris Tankersley stated in his Docker for Developers. And two basic concepts of Docker are image and container, containers to images are what objects to classes as in OOP terminology.

How To Run Bleeding-edge Qtile Within a Virtualenv

Sun, 29 Sep 2019 17:05:00 +0800

For having been using GNOME for quite a long time, I was considering trying some tiling window managers to see what it's like a few weeks ago. Along the way, I found a nice window manager written in Python: Qtile, what interests me most is that it's a hackable window manager, which makes it flexible to extend or change its behaviors.

Well, switching to use a tiling window manager is far simpler than I thought. There are two ways to have it:

How To Revert a Series of Git Commits?

Tue, 24 Sep 2019 23:14:00 +0800

Sometimes, I need to revert a series of commits that I've already pushed, doing a git hard reset (git reset --hard) is not an option, as someone may already have new commits based on mine.

For example, assume that I've made a few commits like below:

65a2c62 * commit 10
25cad43 * commit 9
72ad583 * commit 8
ceebf9a * commit 7
acf8a11 * commit 6
28d526f * commit 5
63af1e2 * commit 4
982c71c * commit 3
0fb4c2d * commit 2
acf9da1 * commit 1
b5f9933 * commit 0

For whatever reason, I need to "drop" the changes made by commit 6 to commit 10, that is, go back to "commit 5" without deleting these commits.

How to Change Web Page Titles Easily

Sun, 18 Aug 2019 14:57:00 +0800

There are times that I need to open many web pages of some specific websites within a browser, and there are so many tabs that I can't efficiently access one of them, as their favicons are all the same.

So I tried to find a way to rename their titles, preferably in a lightweight way, so that I can spot them quickly with my eyes.

The first thought came into my mind was to find some browser extensions to do the job. It was easy to install one with no time. But I was not very happy with the experience. It seems that it keeps the rule of renaming titles based on the URL so that the title will always be renamed if I refreshing it, which is not what I want. I'd rather want to do it in an ad-hoc way.

Generating org-mode Outlines for wikiHow Articles

Sat, 20 Jul 2019 20:04:00 +0800

Recently I found some great articles on wikiHow, then I want to keep notes of them in org-mode files.

At first, I manually copied the ToC of articles, but soon I found it's tedious and takes a lot of time. Today I wrote a requests-based Python script to help me extract the ToCs (Table of Content) into org-mode outlines. It takes two arguments, the first one is the URL, the second one is the containing heading's level for the generated ToC in org-mode.

Understanding align-regexp of Emacs

Sat, 20 Jul 2019 13:50:00 +0800

Emacs' M-x align-regex is neat when I want to align some similar text, especially when we're coding. I use its trivial version(without prefix arg) regularly on day-to-day programming work before.

For example, I can use it to align below code quickly by:

Choose the region
M-x align-regexp and type = and Enter

aaaaaaaaaaaaaa = fields[0]
bbb = fields[1]
cccccccc = fields[2]

It will be aligned to below code, now it's better to read:

aaaaaaaaaaaaaa = fields[0]
bbb            = fields[1]
cccccccc       = fields[2]

A few days ago, I found myself don't understand how it works when I read the code of smart-align, A simple align-regexp wrapper for easier usage. I was confused by the parameters, especially REGEXP and GROUP, and SPACING, here is its signature:

ER Diagrams in Plain Text

Sat, 06 Jul 2019 11:59:00 +0800

If you ever wonder how to plot ER diagrams in plain text, you may have already heard of erd. It's a cool command line program written by Andrew Gallant in Haskell, to "compile" plain text files into nicely looking images, leveraging the power of GraphViz.

I've used erd for some time, it's cool and the syntax is quite simple. It's also quite simple to install it on Linux, just install GraphViz and erd itself, by following the instructions in the README page.

Fine-tune Curly Braces Style of Yasnippet Snippet on the Fly

Sun, 24 Feb 2019 16:48:00 +0800

Yasnippet is a good friend to help us type less and write more, whenever we write some text snippets repeatedly. And there is also an official repository called yasnippet-snippets that contains various snippets for many programming languages (modes), so that we can have many snippets in no time by installing it.

But there is a little problem when it comes to conforming to different coding styles.

Take the if snippet for example, normally it will generate code like this:

Ken Huang

Your Screenshots Deserve Better. Introducing Backdrop.

🥷 Clojure Pro Tip 5: Hiccup Raw

🥷 Clojure Pro Tip 4: Cider ClojureDocs

🥷 Clojure Pro Tip 3: the Thread-As Macro

🥷 Clojure Pro Tip 2: group-by

Collecting Events to Google Analytics using ClojureScript

🥷 Clojure Pro Tip 1: the Discard Reader Symbol

Rewrite of a Flask Web App in Clojure

Intro

Constructing Clojure Maps Conditionally

Getting Started with Cider for Clojure Programming

Jack In to a REPL

Evaluate Things

A Few Quick Notes About babashka/fs

Doing Unit test in Clojure Is Easy

Clj-async-profiler Rocks

TailwindCSS Docs Index

Getting Started

Core Concepts

Customization

Base Styles

Layout

Adding Clojure Dependencies from the Command Line

Bitten by Lazy Sequence of map

Anonymous Functions in Thread Macros

Starting a Clojure nREPL Manually for Cider

Join Every N Lines By A Separator in Emacs

Restoring Emacs' Window Layouts

Emphasize Text By Dragging Mouse in Org-mode

Join Lines By A Separator in Emacs

Hugo Blogging in Emacs

Auto-complete Accounts From Other Beancount Files in Emacs

A Bookmarklet for Copying a Link as an Org-mode Link

Emacs Debugging Techniques

Duplicate the current line in Emacs

Adjust the laptop's screen brightness in Emacs

How to Kill a "Visible" Buffer Quickly in Emacs

How to append items to the CSV file without header row?

About Me

Interesting OSS Projects I Contributed

Interesting Personal Projects

Eglot for Better Programming Experience in Emacs

How to Reload i3status config On the Fly

Language Shadowing with subed in Emacs

Writing a Python Script in Emacs in 45 Minutes!

Intro

Beautiful Soup 4 Cheatsheet

Core concepts (classes)

The Tag class

Clojure reduce: one case for text processing

illustrate.clj to Illustrate Clojure Snippet

String Title Case in Clojure

String Manipulation in Clojure

Send Notifications from Emacs with i3wm and Dunst

A Random Password Generator in Babashka

An Online Python re.findall Service

Generate Call Graphs Using Doxygen in Emacs

Is It Safe to Use Redis As a Data Store?

A Trick to Troubleshoot Emacs Subprocess Creating

ppcompile: An Emacs Package to Help Coding Locally

The Binary Search Idea for Narrowing Down Problem Space

Manage SSH Connections with ~/.ssh/config

Why Can't Git Fetch Remote Branches Other Than Master?

Open New Urxvt from within Emacs

Build Docker Images for Qtile

How To Run Bleeding-edge Qtile Within a Virtualenv

How To Revert a Series of Git Commits?

How to Change Web Page Titles Easily

Generating org-mode Outlines for wikiHow Articles

Understanding align-regexp of Emacs

ER Diagrams in Plain Text

Fine-tune Curly Braces Style of Yasnippet Snippet on the Fly

The `Tag` class