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Tangential but what's the status of garbage collection and DOM manipulation in WASM? Are we ever getting those? I understand it's a high-value technology without them, but I'm interested in writing full apps in say, OCaml (so I'm glad to hear that WASM is getting TCE!).
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WASM doesn't have jumps [1]. And it's not as low-level as you might expect. But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. https://webassembly.github.io/spec/core/syntax/instructions....
I never expected WASM to be low-level to begin with, so I don't believe it could ever possibly be "as low level as I might expect". Something like NaCl (the original one) perhaps could have been called "low level". > But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. I don't see how jumps are "fictional". Plenty of CPUs have them. Even act…
But code is both a mechanical implementation and an abstract, often mathematical, concept. In the concept space, jump is as abstract as call, variable assignment, operator evaluation, etc. A Von Neumann machine is but one way to implement an abstract mathematical / conceptual machine.
In the mathematical space, there's no "high level" vs. "low level," there's just "features a language has" vs. "features it does not." There are other abstractions that are actually harder / impossible to do correctly with jump in the language (stack unwinding comes to mind, which is why C++ solves the exceptions vs. setjmp / longjmp dichotomy by... Not solving it, and a program that uses both will just do something undefined. C++ without setjmp / longjmp would be a language with fewer undefined behaviors).
ELI5: Tail-calls?
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WASM doesn't have jumps [1]. And it's not as low-level as you might expect. But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. https://webassembly.github.io/spec/core/syntax/instructions....
I never expected WASM to be low-level to begin with, so I don't believe it could ever possibly be "as low level as I might expect". Something like NaCl (the original one) perhaps could have been called "low level". > But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. I don't see how jumps are "fictional". Plenty of CPUs have them. Even act…
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Actually, I'm taking another look at TypeScript today. I liked it well enough when I last investigated it in 2016, but the code I wrote then was just a veneer over jQuery. I'm sure things have improved dramatically, which I am about to find out. Frankly, a Turing complete type system [1] seems like over-kill to me and a complication I don't need. Still, Dart had everything I wanted in a front end language in 2013. I…
I highly recommend TypeScript. I don't really like the JS runtime, but, purely from a language point of view, TS is my favorite. Some cool features: 1) Type unions interface A { a: string; } interface B { b: string; } type C = A | B; const c: C = { a: 'a' }; 2) Type assertions if ('a' in c) { /* compiler knows c is of type A here */ } function isA(c: A): c is A { return 'a' in C } // compiler knows c is A if this ret…
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I never expected WASM to be low-level to begin with, so I don't believe it could ever possibly be "as low level as I might expect". Something like NaCl (the original one) perhaps could have been called "low level". > But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. I don't see how jumps are "fictional". Plenty of CPUs have them. Even act…
Jump as a concrete implementation is easy to understand (it's just math on a program counter). But code is both a mechanical implementation and an abstract, often mathematical, concept. In the concept space, jump is as abstract as call, variable assignment, operator evaluation, etc. A Von Neumann machine is but one way to implement an abstract mathematical / conceptual machine. In the mathematical space, there's no "…
[EDIT, from a deleted comment of yours:
> The RISC-V chip is in the same family as the PDP-11 architecture. The Turing machine itself requires no JMP instruction, so it is possible to build a CPU without one. Has anyone done so? In general no, because the PDP-11 had profound impact on the world of physical computing. But one does see it from time to time; GLSL, for example, has no `goto` instruction because the graphics card shader hardware it was built to operate on does its magic by running exactly the same instructions on multiple data; jump would imply the ability for one of the instruction flows to be different from the others in its processing cell, which the hardware cannot support while maintaining the throughput it must to accomplish its task.
I get what you're trying to say here, but sort of a guiding principle for me here for many years has been what I call "the principle of minimal total complexity". While you can keep making the CPU simpler in many cases, if that causes your program to become excessively long in the sense that the total size of the description of your program AND the device it's running on starts actually increasing, that's a place you don't want to design yourself into in practice. In case of sequential machines, I don't consider removal of features that makes programs unnecessarily long "making the machine even more low-level", that's just "making the machine dumber" to me. Feel free to look at the Oberon system (both HW and SW) to see what I have in mind by that -- that seems to be about as minimal a complete system as I can imagine in practice.]
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I never expected WASM to be low-level to begin with, so I don't believe it could ever possibly be "as low level as I might expect". Something like NaCl (the original one) perhaps could have been called "low level". > But even still you're assuming that low level means a specific model of computation a la PDP-11 that's as fictional as any other. I don't see how jumps are "fictional". Plenty of CPUs have them. Even act…
I feel like you're ascribing some judgement to the word fictional, it just means that machines, real or virtual, present programs a model of computation that is an abstraction over the implementation. One such abstraction is the notion of a program that is a block of instructions executed in sequence with a program counter, registers, memory, a stack. But that's not the only abstraction you could imagine. The JVM for…
I'm not saying that "fictional" things are bad. Tail calls themselves are "fictional" to me in the sense that all tail calls are jumps but not all jumps are tail calls, and the distinction between a tail call and a general jump is too difficult to make for a reasonably sized physical machine and best left to the compiler. But that is not me being judgmental against tail calls, of course -- I love tail calls and consider their lack a huge design failure wherever they're absent.
Why not focus on features that would unlock better integration of actual mainstream languages - Java, C#, Python etc.? Let functional programmers discuss monoids on their endofunctor forums or something.
In LLVM C++ coroutines compile down to functions with the "musttail" attribute, that right now is not possible to express in Wasm [1].
It is also useful to efficiently implement stuff like interpreters, where you use it as a way to jump to the code of the next instruction directly (Wasm has only structured control flow, but you can see a tail call as a sort of jump/goto instruction)
[1]: https://discourse.llvm.org/t/supporting-coroutines-without-t...
Tangential but what's the status of garbage collection and DOM manipulation in WASM? Are we ever getting those? I understand it's a high-value technology without them, but I'm interested in writing full apps in say, OCaml (so I'm glad to hear that WASM is getting TCE!).
DOM manipulation hasn't changed - you still need to call into JS to do those. Ideas like WebIDL bindings have been proposed over the years but haven't shown enough benefit. JS is better for DOM-heavy code, while wasm excels at computation-heavy code. But you can write bindings from wasm (maybe someone already has for OCaml?), which is what toolchains do today - not as fast as JS, but often good enough.
Why not focus on features that would unlock better integration of actual mainstream languages - Java, C#, Python etc.? Let functional programmers discuss monoids on their endofunctor forums or something.