Clojure Projects
24 March 2025
Advent of Code
As of the end of 2024,
I’ve done at least some of Advent of Code
for 7 years in a row.
I’ve had the most fun and practice
parsing and transforming
the input data
for each puzzle.
I learned pretty quickly from the puzzles
to store the common grids as sparse maps
to save lots of memory and keep the problem in memory.
I sometimes got stuck on the puzzle and the algorithm,
but I still got lots of practice in general Clojure.
I definitely see that the Clojure data structures
lend themselves well to the puzzles.
I’ve gotten to effectively apply
lots of common Clojure libraries
like core.async and core.logic.
Incidents
My incidents project
scrapes an RSS feed of emergency response incidents
in Lancaster County
and stores them into an XTDB database
for history.
It generates static site of current events with hiccup
and historical charts with Clerk.
Running this project
day-to-day,
I learned that the Clojure/JVM start up
is a bit too heavy to start frequently
from cron,
so I run it as a service in systemd with its own scheduling.
Clerk and the amount of data I’m processing
is also a bit heavy,
so I have that scheduled to rebuild less frequently than the scraper.
The site is still all static.
Event Logger
With this CLJS project,
I was trying to derive a standard shadow-cljs workflow
to make sure I could start any new CLJS web project quickly.
It started using Reagent,
and I migrated to Helix
to be less-insulated from newer React features.
I also wrote code to migrate data
in local browser storage from an old Transit format
to EDN.
I’m constantly learning the better flows
for data in React and local storage.
COVID Warehouse and COVID Web
The data was pretty messy early on,
and it changed over time,
so I needed to parse lots of different formats.
I generated a static site with my historic graphs
and focused on World, US, and counties in Pennsylvania.
It was a classic ETL for a star schema data warehouse,
since I wanted to refresh my experience on that.
I initially stored in in a SQL database
using hugsql and next.jdbc.
After a bit of time,
this became my first project to explore CRUX/XTDB
and NoSQL data structures.
I learned a bit about how changes applied in XTDB
and how to limit history
and otherwise save space
on my small server environment.
I could easily apply core.async
when it was time to get things done faster.
The web app project
that I added later
provided a more dynamic Reagent app in CLJS
that used the static data produced by warehouse project.
Planning Poker
I wanted a simple tool
for conducting planning poker in sprint planning,
so I built one
in JS to run on mobile phones.
When I started learning CLJS,
I converted it to Reagent and used Leiningen to build it.
Clojure All the Other Things!
I’ve enjoyed finding there are ways to apply Clojure to everything!
Structured Intepretation of Computer Programs
Music in Overtone
I have a project
where I play with data structures for music
and explore lots of examples in Overtone,
including Rich Hickey’s experiments in additive synthesis
and sequencing some simple beats
from drum-n-bass tutorials for other DAWs.
It required lots of yak-shaving work over the years to keep
the native wiring to Supercollider and Linux sound working.
Fixes for Overtone and SuperCollider on PopOS 20.10
02 November 2020
I took the update to PopOS 20.10,
and my Overtone setup stopped working.
When I’d try to boot up
the internal SuperCollider server
from Emacs or from the leiningen repl
on my music projects
which all (:require [overtone.live :refer :all]),
get an error in native libraries.
I could also try to start the server
with (boot-internal-server) or (boot-external-server),
but it gives the same error.
--> Booting internal SuperCollider server...
Cannot read socket fd = 107 err = Success
CheckRes error
Could not read result type = 22
Client name = Overtone conflits with another running client
Cannot connect to the server
JackShmReadWritePtr1::~JackShmReadWritePtr1 - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
could not initialize audio.
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f5eec0e9ba7, pid=30517, tid=30605
#
# JRE version: OpenJDK Runtime Environment AdoptOpenJDK (15.0.1+9) (build 15.0.1+9)
# Java VM: OpenJDK 64-Bit Server VM AdoptOpenJDK (15.0.1+9, mixed mode, sharing, tiered, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# C [libscsynth.so.1+0x63ba7] World_WaitForQuit+0x7
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/john/workspace/music/hs_err_pid30517.log
--> Connecting to internal SuperCollider server...
[thread 30576 also had an error]
#
# If you would like to submit a bug report, please visit:
# https://github.com/AdoptOpenJDK/openjdk-support/issues
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
Since it can no longer start the server internally
from within Overtone,
I start the server manually.
I wrapped a script around the start up,
so I can set the environment variables
for configuring jack
and starting up the synth:
#!/bin/sh
# automatically connect up jack ports
export SC_JACK_DEFAULT_INPUTS="system:capture_1,system:capture_2"
export SC_JACK_DEFAULT_OUTPUTS="system:playback_1,system:playback_2"
scsynth -u 57110
To get Overtone going again,
I disabled the automatic boot
of the server within Overtone
by switching all the requires
in each file
from overtone.live to overtone.core,
and I connect
to that external server
from my REPL manually
with (connect-external-server)
before doing anything else.
Finally,
Overtone was consistently
failing to find my MIDI keyboard.
When things were working
well enough a couple months ago,
it still had required
a little dance of killing off jackd
and restarting Overtone,
since something had been
tying up the MIDI interface.
This workaround was no longer adequate,
since scsynth and jackd
needed to already be started.
I disabled MIDI connection in jackd
by removing the -Xseq option
from my ~/.jackdrc.
I’m back in business,
and it’s probably more robust
with these manual steps now.
I think I’m also seeing
some other odd little things working
with the external server
that didn’t previously,
like using (mouse-x)
for reading mouse positions into the synth values.
The built-in piano synth is also
working where it hadn’t previously.
Update 2021-02-13:
I had lost the ability
to send desktop audio (pulseaudio)
through to the Jack Sink
with this setup,
so I figured out
to start qjackctl
before my supercollider.sh.
That gets the Jack Sink
available again to pulseaudio
and the desktop sound menu.
Escape with Spacemacs in Tmux
21 October 2020
I’ve occasionally
been using a SSH session
from my Pixel phones
for years to login
to my servers
and write Clojure code
in Emacs.
I’d often run into an issue
where I find myself
having a weird time
switching between NORMAL and INSERT modes
when I’d hit ESCAPE quickly
and try to move the cursor.
Googling my random problems
is a favorite pastime,
and I’ve finally stumbled
upon an article about
tmux and vim escape key.
I learned
that it’s probably been tmux
sporadically eating my ESCAPE key,
so I’ve tried disabling the built-in delay
by adding to my
.tmux.conf:
Templates and Snippets in Emacs
30 August 2020
I was only trying to write that last article,
but it took me days to finally do it.
I had so much work to do before I got there.
I had come to appreciate Emacs
automatically inserting the boilerplate
namespace declarations in new Clojure files,
and I really thought I needed such convenience
for my blog posts written in AsciiDoc
in JBake.
I dove down a 20-tab-deep,
yak-shaving hole to get it done.
I had to figure out the right search terms
and names for what Emacs was doing for me.
I finally found yatemplate
which seems similar to yasnippets.
Spacemacs
has the templates layer
for integrating yatemplate support,
so I added that layer and created a template
for my adoc files in my .emacs.d directory.
My simple case worked,
but I recognized
that I’ll want that template
on all my machines,
so having a local copy of it
wouldn’t cut it.
I needed a way to check-in and version more Emacs/Spacemacs files
than just my ~/.spacemacs files I was previously distributing.
I learned yasnippets would default
to looking in ~/.spacemacs.d/
if the configuration was in there,
so I had to move my ~/.spacemacs file
over to ~/.spacemacs.d/init.el.
To have the templates layer source templates
from the .spacemacs.d directory,
it required an extra bit of configuration
when introducing it to the dotspacemacs-configuration-layers:
(templates :variables templates-private-directory "~/.spacemacs.d/templates")
At this point,
I could now commit
my .spacemacs.d directory
with the regular configuration file
and the supporting templates and snippets.
All those files will be cloned
to all my workstations.
I was almost ready to write
that article,
but yasnippet and yatemplate
have this fancy templating language.
I’m sure that can make
my article-creation even smarter!
I read a bit more
and found a couple cool elisp functions
for automatically filling in the date
and building a title
from the file name.
With the final enhancements
to my adoc template,
I could write the article,
if I could only remember
what I was trying to do
in the first place.
I hope to at least remember
how to use these snippets and templates
for future work.
All the Posts
March 2025
November 2020
October 2020
August 2020