nelson VS Duktape

Nelson is an array programming language providing a powerful open computing environment for engineering and scientific applications using modern C/C++ libraries (Boost, Eigen, …) and others state of art numerical libraries. It has sophisticated data structures (including cell, struct, linear systems, …), an interpreter and a high level programming language. Nelson has been developed to be an open/modular system where an user can define these own data types and operations on these data types by using overload. For more information go to https://nelson-numerical-software.github.io/nelson-website/.

Nelson is an array programming language providing a powerful open computing environment for engineering and scientific applications using modern C/C++ libraries (Boost, Eigen, …) and others state of art numerical libraries. It has sophisticated data structures (including cell, struct, linear systems, …), an interpreter and a high level programming language. Nelson has been developed to be an open/modular system where an user can define these own data types and operations on these data types by using overload. For more information go to https://nelson-numerical-software.github.io/nelson-website/.

Nelson is an array programming language providing a powerful open computing environment for engineering and scientific applications using modern C/C++ libraries (Boost, Eigen, …) and others state of art numerical libraries. It has sophisticated data structures (including cell, struct, linear systems, …), an interpreter and a high level programming language. Nelson has been developed to be an open/modular system where an user can define these own data types and operations on these data types by using overload. For more information go to https://nelson-numerical-software.github.io/nelson-website/.

Nelson is an array programming language providing a powerful open computing environment for engineering and scientific applications using modern C/C++ libraries (Boost, Eigen, …) and others state of art numerical libraries. It has sophisticated data structures (including cell, struct, linear systems, …), an interpreter and a high level programming language. Nelson has been developed to be an open/modular system where an user can define these own data types and operations on these data types by using overload.

You can also refer to the Unicode routines of other small JS engines[1,2], those don’t use ICU either, although the implementations are mercilessly size-optimized (to put it politely) and restricted to what the target JS version requires (e.g. casemapping but no normalization).

[1] https://github.com/bellard/quickjs/blob/master/libunicode.c

[2] https://github.com/svaarala/duktape/blob/master/src-input/du...

> memcpy from bytes to a NaN should work fine

Signaling NaNs are explicitly undefined in C11 F.2.1.: "This specification does not define the behavior of signaling NaNs." - and in practice may be "quieted" by conversion to Quiet NaNs, changing their bit patterns. Fast math optimization flags will also break the hell out of your code by assuming NaNs are impossible. I want to say there are more circumstances where optimizers and compiler generated code can butcher your NaN payloads, but I'd be working off recollected hearsay and I can't find a source, so don't quote me on that.

NaN boxing is common enough that, if you take the right precautions, a modern compiler should probably support it, maybe. NaN boxing is uncommon enough that, if your codebase needs to be sufficiently portable, you need an opt out for when it breaks. Let's review duktape's scars:

https://github.com/svaarala/duktape/blob/123d9426d5e5b36d5da...

https://github.com/svaarala/duktape/blob/5252b7a50611a3cb8bf...

https://github.com/svaarala/duktape/blob/224a0b89ca08a36e37e...

Note that "the right precautions" involve unions and proper integer types to avoid optimizer-invoked rewrites of the value and debugging when things go wrong, not simply YOLOing bytes into a double via memcpy. Note that debugging when it all goes terribly wrong can be quite painful. I've personally had the misfortune of being forced to debug duktape being built with fast math optimizatoins enabled on one "rare" platform + build configuration that wasn't caught by duktape's #if defined(__FAST_MATH__) checks linked above (wasn't Clang nor GCC, so go figure it didn't make the same #define)

I was expecting this to be about Duktape <https://github.com/svaarala/duktape>, but heh, for sure no. I'd bet $1 there's no way youtube-dl would switch, but I wonder if yt-dlp would?

- Duktape (4.8k stars)