Turnstyle
Published on August 21, 2024 under the tag haskell
I am delighted and horrified to announce a new graphical programming language called Turnstyle. You can see an example below (click to run).
In the time leading up to ZuriHac 2024 earlier this year, I had been thinking about Piet a little. We ended up working on something else during the Hackathon, but this was still in the back of my mind.
Some parts of Piets design are utter genius (using areas for number literals, using hue/lightness as cycles). There are also things I don’t like, such as the limited amount of colors, the difficulty reusing code, and the lack of a way to extend it with new primitive operations. I suspect these are part of the reason nobody has yet tried to write, say, an RDBMS or a web browser in Piet.
Given the amount of attention going to programming languages in the functional programming community, I was quite surprised nobody had ever tried to do a functional variant of it (as far as I could find).
I wanted to create something based on Lambda Calculus. It forms a nice basis for a minimal specification, and I knew that while code would still be somewhat frustrating to write, there is the comforting thought of being able to reuse almost everything once it’s written.
You can see the full specification here.
After playing around with different designs this is what I landed on. The guiding principle was to search for a specification that was as simple as possible, while still covering lambda calculus extended with primitives that, you know, allow you to interact with computers.
One interesting aspect that I discovered (not invented) is that it’s actually somewhat more expressive than Lambda Calculus, since you can build Abstract Syntax Graphs (rather than just Trees). This is illustrated in the loop example above, which recurses without the need for a fixed-point combinator.
For the full specification and more examples take a look at the Turnstyle website and feel free to play around with the sources on GitHub.
Thanks to Francesco Mazzoli for useful feedback on the specification and website.