pdubroy
Joined 18 years ago
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http://dubroy.com/blog - on programming, usability, and design
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Comment · 7 months ago
From https://ohmjs.org —
Here are some awesome things people have built using Ohm:
- Shopify's theme-tools (https://github.com/Shopify/theme-tools/), used in their online code editor and the official VS code extension.
- Seymour (https://github.com/harc/seymour), a live programming environment for the classroom.
- Shadama (https://tinlizzie.org/~ohshima/shadama2/live2017/), a particle simulation language designed for high-school science.
- Slang (http://slang.kylestetz.com/), a browser-based audio programming language, and turtle.audio, a music sequencer inspired by turtle graphics programming.
- Simpletalk (https://github.com/dkrasner/Simpletalk) is an expressive, programmable authoring system inspired by Hypercard and Smalltalk. (See also the StrangeLoop talk).
- Wildcard (https://www.geoffreylitt.com/wildcard/), a browser extension that empowers anyone to modify websites to meet their own specific needs, uses Ohm for its spreadsheet formulas.
- JAMScript (https://citelab.github.io/JAMScript/) is a programming language for edge-based IoT applications.
- Bruno (https://github.com/usebruno/bruno) is an open source IDE for exploring and testing APIs.
It has also been used in a number of projects by Ink & Switch (https://inkandswitch.com), including Potluck (Dynamic documents as personal software: https://www.inkandswitch.com/potluck/), the Deja Vu project at MIT (https://sdg.csail.mit.edu/project/deja-vu/), ...
Comment · 9 months ago
Shameless plug: if you're interested in learning WebAssembly — like really learning the bytecode format and how it works — you might like our book, WebAssembly from the Ground Up: https://wasmgroundup.com.
It starts with handcrafted bytecode for a minimal Wasm module in JavaScript, and then guides you through the creation of a simple compiler for a toy language.
Comment · 10 months ago
I know there have been solutions in the Java world for >20 years, though I can't comment on well they work in practice.
From a quick search, _An Implementation of Scoped Memory for Real-Time Java_ (https://people.csail.mit.edu/rinard/paper/emsoft01.pdf) provides a decent overview:
> Real-Time Java extends this memory model to support two new kinds of memory: immortal memory and scoped memory. Objects allocated in immortal memory live for the entire execution of the program. The garbage collector scans objects allocated in immortal memory to find (and potentially change) references into the garbage collected heap but does not otherwise manipulate these objects.
> Each scoped memory conceptually contains a preallocated region of memory that threads can enter and exit. Once a thread enters a scoped memory, it can allocate objects out of that memory, with each allocation taking a predictable amount of time. When the thread exits the scoped memory, the implementation deallocates all objects allocated in the scoped memory without garbage collection. The specification supports nested entry and exit of scoped memories, which threads can use to obtain a stack of active scoped memories. The lifetimes of the objects stored in the inner scoped memories are contained in the lifetimes of the objects stored in the outer scoped memories. As for objects allocated in immortal memory, the garbage collector scans objects allocated in scoped memory to find (and potentially change) references into the garbage collected heap but does not otherwise manipulate these objects.
> The Real-Time Java specification uses dynamic access checks to prevent dangling references and ensure the safety of using scoped memories. If the program attempts to create either 1) a reference from an object allocated in the heap to an object allocated in a scoped memory or 2) a reference from an object allocated in an outer scoped memory to an object allocated in an inner scoped memory, the specification requires the implementation to throw an exception.
Comment · 11 months ago
Awesome! You're exactly the kind of person we were thinking of when we wrote the book…experienced programmers who are interested in understanding things at a lower level.
Let us know how it goes! You can find us in the book Discord, or email us at [email protected].
Comment · 11 months ago
Edit: changed slightly to provide a more useful answer.
No, it doesn't — not this version of the book at least. We only cover WebAssembly 1.0.
That said, as my co-author says below, there's really not much to tail calls. Once you've worked through the book, you'd be able to grok tail calls pretty quickly.
As an aside — 2.0 was announced just a few weeks after we launched the book, and 3.0 a few months ago. And with 3.0 (which added tail calls), the spec has more than doubled in size vs 1.0, so it would be hard to cover everything.
We've talked about doing a new chapter to cover some of the interesting parts of 2.0 (e.g. SIMD), but covering everything in 3.0 (garbage collection, typed reference, exception handling, tail calls…) feels almost like an entire 2nd book!
Comment · 11 months ago
I agree, it really is quite approachable.
Comment · 11 months ago
Ah, good catch! I see them in one of the screenshots. Those are just inlay hints, they're not in the source code. (The editor is https://zed.dev)
Comment · 11 months ago
Thank you!
I would 100% agree that the spec is quite readable. At the top of our Minimum Viable Compiler chapter, we say:
> The binary module format is defined in the WebAssembly Core Specification. You’ll notice that we back up many of our explanations with reference to the relevant part of the spec. One of our goals with this book is to convince you that the spec is a valuable resource that’s worth getting familiar with.
I think the spec is great as reference material, but we wrote the book to be more of a tutorial. We've talked to many people who say they've looked at the spec, but find it too overwhelming. For those people, we hope the book provides a good structure that ultimately helps them become comfortable with the spec!
Comment · 11 months ago
Yes, it can all be found here: https://github.com/wasmgroundup/code
Over the course of the book, we also build up a small library for creating Wasm modules and emitting bytecode; that's available as an NPM package (https://www.npmjs.com/package/@wasmgroundup/emit) and the code is here: https://github.com/wasmgroundup/emit
Comment · 11 months ago
Hi HN! Co-author of the book here, happy to answer any questions you have.
Beyond the sample chapters which are linked from the landing page, we also have a couple blog posts which may be interesting:
- A WebAssembly Interpreter: https://wasmgroundup.com/blog/wasm-vm-part-1/
- An older blog post, "A WebAssembly compiler that fits in a tweet" (https://wasmgroundup.com/blog/wasm-compiler-in-a-tweet), was also on HN earlier this year: https://news.ycombinator.com/item?id=42814948
Comment · 11 months ago
It's explained in the post:
> Then, my plan was to construct a ProseMirror transaction that would turn the old tree into the new one. To do that, it’s helpful to know which nodes appeared in the old document, but not the new one.
So, it's not actually about reclaiming the memory. It's about taking some action on the nodes that will be reclaimed. It's akin to a destructor/finalizer, but I need that to happen synchronously at a time that I control. JavaScript does now support finalization (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...) but it can't be relied on to actually happen, which makes it useless in this scenario.