Declarative WebGPU with S-Expressions

8/24/2026 at 2:01:48 AM

I am a big Lisper. You lost me at the triple quote.

by SomeHacker44

8/24/2026 at 9:28:09 AM

hey! indeed, it is a pattern more from Python/Kotlin/etc and on first sight it looks awful for those used to work in more lispy ways.

pngine is using a data language I made for fun with s-expressions and appropriately named "SJON". It is a data language (kinda like EDN, or er.. JSON) to declare things, not to run/interpret things, it has no reader macros, no quote/unquote, no eval, no cons or car/cdr or..., the only thing similar to Lisp is really the surface look, and on the surface triple quotes really feel like they don't belong in there.

But I need to paste WGSL into a config file and WGSL can be full of " and \, and I have no reader to extend.

In a way I'm glad you didn't spend a lot of time and got lost at the start ahah because if the triple quote bothered you the rest would too.

For instance, in SJON strings don't remember their quotes:

  (= """hello""" "hello")     ; true
  (= "a\nb" """a
  b""")                       ; true, escapes resolve before comparison

It is a data language, and one thing I wanted was for numbers to carry their units:

  (camera :ortho :zoom 2 :fov 90deg :shutter 250ms :scale 50%)
  ; unit is a suffix glued to a number with no space
  ; oh! and dates and times are also token kinds: 2026-05-19 and 23:59:59.999 lex as values
  ; these don't get interpreted, just carried over and then the schema decides what is valid

yeah... there is a schema, which is written in SJON too, that is validated ahead of evaluation, and docs have a binary IR, so a tiny runtime can consume one without carrying a parser.

For instance, the SJON schema for the WebGPU spec was sketched from the spec API.

Sorry for the long answer, yeah, it is not Lisp, just S-expressions to leverage a small part of their amazing versatility.

by hugodan

8/24/2026 at 9:07:50 AM

Needs a Lisp Shading Language.

by lrasinen

8/24/2026 at 9:32:56 AM

ahah indeed! when I was young someone or something etched into my tiny brain that "thou shalt never abstract a DSL, it is wrong!".

I think I should have outgrown this by now, there is some truth to it but I feel it is certainly not absolute at all, and this is essentially a for fun project with no rules or greater intent beyond that.

by hugodan

8/24/2026 at 6:03:42 AM

The triple quote screams scrambled eggs with bacon.

by larodi

8/24/2026 at 9:33:30 AM

hahah loved this one! so true, can I have a bit of onion too?

by hugodan

8/24/2026 at 12:47:50 AM

Looks interesting but none of the examples worked on the latest iOS safari

by shevis

8/24/2026 at 9:41:53 AM

I'm sorry they aren't working for you :(

I am running ios 26.6 in iphone mini. Do you know the version and device model where they are failing for you? (in Settings -> General -> Info)

by hugodan

8/24/2026 at 1:26:30 AM

They all worked for me in iOS safari..

by k33n

8/24/2026 at 10:22:05 AM

You can try to make the WebGPU API more declarative, but the issue that you still run into is that individual draw calls and passes are a poor abstraction level to express modern rendering in.

To reach the quality of a modern PBR renderer with shadows, SSAO, temporal denoising and the like, you need to lower one conceptual draw into multiple concrete draws, sequenced in a particular way, to their own targets, and I haven't seen a lot of success in this space because the shaders need to become polymorphic.

by unconed

8/24/2026 at 4:33:14 PM

Hi unconed!

these are very good points, with my attempt the only run-time polymorphism is a switch inside a shader. Maybe we can exploit the pipeline constants and then branch on them, still feels like a hack, but could work for a poor man approach.

I have never done advanced/modern rendering things, just 2D/vector/sdfs and hacks, but your comment is food for thought, in that in this level of abstraction these are somewhat open problems.

by hugodan