awesome! I have wanted something like this for a long time. Currently I use a janet fork <https://github.com/eshrh/matsurika> with some trivial additions, the most important of which is a `$` macro that does what the `sh` does here. I have two questions:
- I see that `sh` does not take in strings but instead lisp forms. How do you distinguish between variables that need to be substituted and commands? In my fork, the way to do variable substitution involves quasiquoting/unquoting.
- Almost all of the features that make your language good for shell scripting are essentially syntactic features that can easily be implemented as a macro library for say, scheme. Why'd you choose to write in C++? Surely performance is not an important factor here. (I'm interested because I am currently working on a scheme-based shell scripting language).
can you give an example of how variable substitution in your language looks like?
one of the things i think a lisp for shell should have, and i agree that this may not be easy, but unix commands should be first class functions, as in, you should not need a $ or sh macro to make them work. the other thing is that strings should not be quoted, and so you need something else to designate variables like $path or ($ path)
Yes, i agree that unix commands should be first class. I did this for the super common stuff like ls and cp. As for substitution, I did exactly $ for substitution. You'd do something like ($ rsync -avP $src $dst), but I don't think I ever got around to implementing $() to evaluate forms. If you really need to do that then you have to quasiquote the whole expression and unquote the form you need to evaluate. This has been relatively ok for me though. I never implemented anything like pipes or redirection, I instead just send everything like that to bash.
This is not really relevant to your question, but I regret choosing janet for this, it's too opinionated and hacking on C is not as fun as lisp. I started writing my own version of schemesh in racket, but I never got far enough.
A lot of wifi sensing results that have high-dimensional outputs are usually using wideband links... your average wifi connection uses 20MHz of bandwidth and is transmitting on 48 spaced out frequencies. In the paper, we use 160MHz with effectively 1992 input data points. This still isn't enough to predict a 3x512x512 image well enough, which motivated predicting 4x64x64 latent embeddings instead.
The more space you take up in the frequency domain, the higher your resolution in the time domain is. Wifi sensing results that detect heart rate or breathing, for example, use even larger bandwidth, to the point where it'd be more accurate to call them radars than wifi access points.
Think of it as an img2img stable diffusion process, except instead of starting with an image you want to transform, you start with CSI.
The encoder itself is trained on latent embeddings of images in the same environment with the same subject, so it learns visual details (that are preserved through the original autoencoder; this is why the model can't overfit on, say, text or faces).
I think the results here are much less important and surprising than what some people seem to be thinking. To summarize the core of the paper, we took stable diffusion (which is a 3-part system of an encoder, u-net, decoder), and replaced the encoder to use WiFi data instead of images. This gives you two advantages: you get text-based guidance for free, and the encoder model can be smaller. The smaller model combined with the semantic compression from the autoencoder gives you better (SOTA resolution) results, much faster.
I noticed a lot of discussion about how the model can possibly be so accurate. It wouldn't be wrong to consider the model overfit, in the sense that the visual details of the scene are moved from the training data to the model weights. These kinds of models are meant to be trained & deployed in a single environment. What's interesting about this work is that learning the environment well has become really fast because the output dimension is smaller than image space. In fact, it's so fast that you can basically do it in real time... you turn on a data collection node and can train a model from scratch online, in a new environment that gets decent results with at least a little bit of interesting generalization in ~10min. I'm presenting a demonstration of this at Mobicom 2025 next month in Hong Kong.
What people call "WiFi sensing" is now mostly CSI (channel state information) sensing. When you transmit a packet on many subcarriers (frequencies), the CSI represents how the data on each frequency changed during transmission. So, CSI is inherently quite sensitive to environmental changes.
I want to point out something that most everybody working in the CSI sensing/general ISAC space seems to know: generalization is hard and most definitely unsolved for any reasonably high-dimensional sensing problem (like image generation and to some extent pose estimation). I see a lot of fearmongering online about wifi sensing killing privacy for good, but in my opinion we're still quite far off.
Is there a survey of SoTA of what can be achieved with CSI sensing you would recommend?
What is available on the low level? Are researchers using SDR, or there are common wifi chips that properly report CSI? Do most people feed in CSI of literally every packet, or is it sampled?
Now many people use https://ps.zpj.io/ which supports some hardware including SDRs, but I must discourage using it, especially for research, as it's not free software and has a restrictive license. I used https://feitcsi.kuskosoft.com/ which uses a slightly modified iwlwifi driver, since iwlwifi needs to compute CSI anyway. There are free software alternatives for SDR CSI extraction as well; it's not hard to build an OFDM chain with GNUradio and extract CSI, although this might require a slightly more in-depth understanding of how wifi works.
I wrote something similar on a smaller scale for the keihin-kyuukou line in japan: https://rail.esrh.me. Now I live in tokyo and there's several transit options closeby so I would love to have some always on display like this in my room.
Unfortunately, while public transit in the US and Europe seem to be tracked by services with developer friendly APIs, this is not the case in Japan as far as i know -- not that much of a problem back then, i just needed to do some light web scraping.
I wrote all of the scraping/data and processing/frontend code in clojure and clojurescript, and wrote a small blog post about it here: https://esrh.me/posts/2023-03-23-clojure
One thing is that CL has a huge ecosystem and a wide variety of compilers for every purpose you might have. Quicklisp probably beats racket and scheme in this regard, but today clojure might have an edge.
When you use racket and clojure specifically, you're kind of walling yourself into one compiler and ecosystem (two, for clj/cljs). This is a significant disadvantage compared to scheme and CL.
CL the way most people write it is way too imperative and OO for me; it reads like untyped java with metaprogramming constructs. Clojure and scheme in my opinion guide you towards the more correct and principled approaches.
Out of all the lisps, regardless of which ones I like the most, I objectively write emacs lisp the most. This is has definitely influenced my opinions on CL syntax; like my weird love hate relationship with the loop macro: on one hand it's a cool, tacit construct that's impossible in a non-lisp, but on the other hand it hides a lot of complexity and is sometimes hard to get right.
> Smile 3.x is GPL-licensed, which poses some potential conflicts for some end users...The community consensus is converging around moving away from Smile due to the GPL-relicensing issue, focusing instead on Tribuo...
(tribuo is developed by oracle)
It's a really great thing that the java community has a high performance and well accepted (~5x stars than tribuo) ML package that's GPL. CF python where the top two libraries are developed by google and facebook. The GPL protects individual, independent developers.
I don't think it's right to recommend that new users move away from the package because of licensing issues; the fact that it's GPL now is a good thing for everyone except corporate users (probably a great part of readers). The people who might have GPL problems already know themselves when they'll have a problem.
I think if you are going to change license, especially in a way that makes it less permissive, you need to be super open and clear about both the fact you are doing it and your reasons for that. This is done so silently as to look like it is intentionally trying to mislead and trick people.
So maybe I wouldn't say to move away because of the specific license, but it's legitimate to avoid something when it's so clearly driven by a single entity and that entity acts in a way that isn't trustworthy.
Yeah.. I have all the respect in the world for Haifeng's talent and I totally understand (and agree!) that open source developers need to be compensated one way or another, and I don't want to get into a debate that could lead to accusations by people who don't know the full story, but there are definitely some sour grapes over the whole situation and some of the pull away from smile has more to do with feelings that not everyone involved is acting in good faith more than issues about GPL exactly.
I don't disagree at all, but unfortunately it's mostly out of the hands of any community to recommend or enforce usage of a given library. There are many valid concerns around GPL licensing (not that I necessarily agree with them), but ultimately ignoring the requirement of many orgs to not use GPL-licensed code would just harm the ecosystem.
After visiting your link I've been looking for a while to see newer drawings from Tanaka, but they've lost the domain for their architecture studio site, and he has the same name than Godzilla's creator, so it took me a while but here's his updated studio site, where you can find more drawings on the "works" section.
- I see that `sh` does not take in strings but instead lisp forms. How do you distinguish between variables that need to be substituted and commands? In my fork, the way to do variable substitution involves quasiquoting/unquoting. - Almost all of the features that make your language good for shell scripting are essentially syntactic features that can easily be implemented as a macro library for say, scheme. Why'd you choose to write in C++? Surely performance is not an important factor here. (I'm interested because I am currently working on a scheme-based shell scripting language).