Quick notes on using CEPL on macOS
Just jotting down some notes while trying to get CEPL working on my oldish MacBook Pro running El Capitan.
- Use SBCL. I usually default to ClozureCL, but for the moment I can’t get
swank:*communication-style* nilto work with it, and things will just break horribly if you end up off the main thread in CEPL. SBCL works fine.
- To make sure that Swank starts up with the right communication style, I stuck this in
#+sbcl (setf swank:*communication-style* nil)
- My (old) Macs only support up to version 3.3 OpenGL contexts, but the version of CEPL that’s available in Quicklisp uses 4.1 contexts. The current HEAD on Github lets you choose your context version, so you’ll need to clone the CEPL repository and some of its dependencies locally in your Quicklisp local-projects directory. (list below)
- Download the runtime frameworks for SDL2 and SDL2_image and stick
- I’m haven’t been able to get the examples running directly yet: it seems like cepl.sdl2’s host step function is getting clobbered by the one in cepl.skitter.sdl2, so you need to avoid loading that.
Repositories you’ll need to clone locally:
- cepl - https://github.com/cbaggers/cepl.git
- cepl.sdl2 - https://github.com/cbaggers/cepl.sdl2.git
- cepl.skitter - https://github.com/cbaggers/cepl.skitter.git
- rtg-math - https://github.com/cbaggers/rtg-math.git
- varjo - https://github.com/cbaggers/varjo.git
Actually running it in SLIME:
- Once you have your
.swank.lispset up, and Emacs configured to use SBCL, start SLIME as normal. (e.g. M-x slime)
- Load cepl.sdl2:
- Initialize CEPL, passing it a window size and the OpenGL context version you need:
(cepl:repl 480 320 3.3)
- If everything went well, you should have a blank, untitled window somewhere on your desktop, probably behind your Emacs window. Clicking on the SBCL icon on your dock won’t bring it forward, you’ll have to go looking for it.
Again, I can’t get the examples to run directly, but you can run the triangle example below by:
- Loading livesupport:
(ql:quickload "livesupport"). The examples use it to keep your REPL usable while Swank is in single-threaded mode.
- Load the example listed below.
(triangle::run-loop)to start it, and hit enter an extra time to get your REPL back.
(triangle::stop-loop)to stop it.
Quickie - Using SQLite4Java from Clojure
We use SQLite4Java at work, and I’m playing around with our databases from Clojure at the moment and just wanted to quickly jot down how to do it.
First, native library management in SQLite4Java is a little hairy: it’s going to look
for the libraries either in
the SQLite4Java jar file, or you can explicitly tell it where to find things. The
Maven config to do this automatically is suitably ugly, and as far
as I know, there’s not a good way to do the same thing with Leiningen.
I opted to just explicitly tell it for now. I list the SQLite4Java dependency in my
project.clj, copied the native libraries I’m interested in into
and then just added this at startup time:
(I’m leaving all of the namespace components in there to be explicit: I require/import them as normal in my code.)
Next issue: actually running queries against a database has to be done using a SQLiteConnection instance, and those instances are limited to being used from the thread that created them. That precludes using them from the REPL: you don’t have any control over what thread your expressions are going to be executed from. So, you need to use SQLiteQueue, which wraps a SQLiteConnection and ensures all calls come from a single thread.
SQLiteQueue works by taking SQLiteJob instances (basically just a function) and running them in first-in-first-out order. Unfortunately, SQLiteQueue can’t just take a Callable, so you can’t use Clojure functions directly. Wrapping a function up in a job is pretty easy though, and is the first time I’ve needed to use clojure.core/proxy:
Then using those jobs is done by calling SQLiteQueue::execute, which returns the job again. Those jobs implement Future, so you can use them as normal, or they have a convenience method SQLiteJob::complete that deals with exceptions for you.
So all bundled together, my little library for working with SQLite4Java looks like this right now:
Boot as a sort-of Quicklisp
Really quick: after dismissing Clojure for years (I have Common Lisp, I don’t care about the JVM, why do I need it?) I finally took the time to learn it about a year ago and OMG I love it and I want to use it for everything (much to the dismay of my team at work).
One of the pain points though is how project-based everything seems to be: if you want to pull in any sort of third party library, you have to build some sort of project, be it Maven, Leiningen, or something similar. List the libraries you want to pull in there and start (or restart) your REPL before you can use them.
Coming from Quicklisp, it’s super annoying, especially if you just want to give something a quick spin.
Enter Boot! It’s a relatively new way to handle building Clojure projects, but it allows you to easily name dependencies when you run it, like so:
That gives me a REPL with Gson loaded and ready to use.
To make life a little easier, I have a task in my
pulls in the dependencies Cider needs:
So when I want to tool around with something, I just run
boot -d whatever:version cider repl,
fire up Emacs, connect and go to work.
I haven’t take the time to get comfortable with Boot for full projects yet, so I’m still using Leiningen for most things, but I love it for quick one-off experiments. It’s not as good as being able to load whatever I want from the comfort of the REPL, but it makes things a lot less painful.
Do I really need that database?
I’m pretty sure that every time I’ve built a web application of any sort in the last decade, I’ve reached for a database. Usually SQLite, at least to start, because it lets me get going fast without any infrastructure in place. It’s not even a question, really: if I’m building a web app, it needs a database of some kind behind it.
Actually, let me rewind just a smidge. I really dig Clojure lately, and my favorite thing about it are the immutable data structures: once you’ve created your map, or vector, or whatever, you can’t change it. Instead, you can derive new things from it. Now that I’m comfortable working with immutable by default things, working without them feels almost like I’m building on shaky foundations.
9 years and counting
Today is my and Jackie’s 9 year anniversary.
It’s funny how things work out. Around when we got married, we had this vague plan to move away from Southern California, to try living other places, to travel a bit and see the world before we really settled down to have kids.
After a year or so it was pretty obvious we weren’t going to do it anytime soon, and we didn’t want to wait forever to have kids, so we had Kayla. Talk about turning our world upside down. Suddenly owning a house became critically important, even if it meant moving well away from work. Suddenly, even though we planned for Jackie to go back to work, we were going to have to get by on just my salary.
Suddenly we were responsible for a child. For a human being. The day Kayla was born, when I went down to the cafeteria alone to get a bite to eat, I cried at how overwhelming it all was.
Somehow, we’ve pulled it off so far. Bought a house 6 months after Kayla was born. 9 months after that we decided she shouldn’t grow up alone, and 9 months after that Colin showed up. The kids are 7 and 5 now, Jackie hasn’t had to go back to work, and we’re still making it. It’s been hard, and continues to be hard, but we’re making it.
Most important: we’re happy.
9 years and counting. We make a pretty good team, Jackie. I love you.
Here’s to many, many more.