All regular expressions are deterministic final automata https://en.wikipedia.org/wiki/Deterministic_finite_automaton (finally, a use for my CS course); the extent to which that counts as a virtual machine varies. Some of the regex syntaxes extend it in ways which don't fit in a DFA and do count as a VM; Perl-compatible RE used to be popular (e.g. in Exim).
Interesting. Not that surprising that it works like this. But isn't it a little surprising that things like regexes, printf syntax and other DSLs aren't mostly handled and parsed at compile time in 2026?
Kind of language-dependent since regexes are normally specified as strings and most languages are pretty weak at "run this code at compile time". One of the things Rust users are fond of.
I have also built a C# source generator myself (XML parser generator), but the developer experience is a bit of a hill to climb compared to what it could be.
I've got subleq+eforth (https://github.com/howerj/muxleq) running in JS
which is dead simple to do. No input but I could output
ASCII mapping values to an array.
Some other examples:
- ACPI configuration for power management and platform stuff [1]
- Bitcoin transactions [2]
- TrueType fonts [3]
[1] https://wiki.osdev.org/AML
[2] https://en.bitcoin.it/wiki/Script
[3] https://learn.microsoft.com/en-us/typography/opentype/spec/t...
There is one in golang regular expressions https://swtch.com/~rsc/regexp/regexp2.html
I guess that is why you say re.Compile.
All regular expressions are deterministic final automata https://en.wikipedia.org/wiki/Deterministic_finite_automaton (finally, a use for my CS course); the extent to which that counts as a virtual machine varies. Some of the regex syntaxes extend it in ways which don't fit in a DFA and do count as a VM; Perl-compatible RE used to be popular (e.g. in Exim).
Inded:
https://wiki.xxiivv.com/site/rewriting.html
That goes back to Ken Thompson's NFA regex interpreter from 1968 [1], [2], [3]. Note: that whole regex series by Russ Cox [4] is great.
[1] https://dl.acm.org/doi/10.1145/363347.363387 -- Programming Techniques: Regular expression search algorithm
[2] https://swtch.com/~rsc/regexp/regexp1.html -- Regular Expression Matching Can Be Simple And Fast
[3] https://swtch.com/~rsc/regexp/regexp2.html -- Regular Expression Matching: the Virtual Machine Approach
[4] https://swtch.com/~rsc/regexp/ -- Implementing Regular Expressions
Interesting. Not that surprising that it works like this. But isn't it a little surprising that things like regexes, printf syntax and other DSLs aren't mostly handled and parsed at compile time in 2026?
Kind of language-dependent since regexes are normally specified as strings and most languages are pretty weak at "run this code at compile time". One of the things Rust users are fond of.
C# is in the middle on this one, where specific features get compile-time support and regex is one of them: https://www.devleader.ca/2026/05/03/c-regex-performance-gene...
I have also built a C# source generator myself (XML parser generator), but the developer experience is a bit of a hill to climb compared to what it could be.
Quake had it’s own vm also
RarVM was used in a previous version of the format, newest RAR has removed it, and RarV5 doesn't have a VM.
This list is entirely incomplete without mentioning Java Card.
There is a tiny Java Bytecode VM in an insanely large list of places, you can find some of them here:
https://github.com/crocs-muni/javacard-curated-list https://en.wikipedia.org/wiki/Java_Card
TikTok shipping XOR cipher'd bytecode & interp is right up there: https://news.ycombinator.com/item?id=34109771
VM for obfuscation is a whole thing. Denuvo has a particularly complicated one https://connorjaydunn.github.io/blog/posts/denuvo-analysis/
Other game examples using VMs not for obfuscation: Z-machine and SCUMM-VM.
yt-dlp's jsinterp.py
https://jxself.org/compiling-the-trap.shtml
I've got subleq+eforth (https://github.com/howerj/muxleq) running in JS which is dead simple to do. No input but I could output ASCII mapping values to an array.
https://esolangs.org/wiki/Subleq
So, yes. yt-dlp runs propietary Youtube JS code defying the original purpose.