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Fun with C++26 reflection: Keyword Arguments

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Re: Fun with C++26 reflection: Keyword Arguments

#41

Post by eqvinox »

hyperhello wrote: post #31
anon-3988 wrote: post #5

I just don't understand why some people are so fascinated by this. Can you all admit that this is not at all practical? I swear C++ folks like it for the sake of it. No other engineer do this. Only antiques people or whatever. Can you imagine an engineer that is adamant on using his mystifying bespoke tool instead of just using a ruler. "But what if I have to measure it in the 4th dimension!?". I was expecting someth…

At this point, you should just switch to JavaScript. The desperation to have the simple ease of JavaScript without having to say you're going near "that terrible language" is twisting C++ into ridiculous loops. I'm serious. It's like a bizarre Victorian relic now.

https://javascriptwtf.com/

Arguably this is worse than C++ because for basic things/beginner to intermediate users, the footguns in C++ are more benign (e.g. performance related, rather than correctness) than the ones in JavaScript.

Re: Fun with C++26 reflection: Keyword Arguments

#42

Post by eqvinox »

AlotOfReading wrote: post #16
anitil wrote: post #14

Earlier quoted context omitted.

Oh I thought that was a C99 addition? It's been a while since I've used them. Edit: struggling to find a source, though this GCC doc suggests it's C99 (but maybe that's only GCC?) - https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html

It was C99. It took C++ 21 years to copy it.

It's been the primary and most annoying interop issue for us when we have to integrate C++ code into our primarily C codebase (= build some pieces of our code in C++, which necessarily has to interact with at least our header files).

(Second place: differences in available GCC/clang compiler extensions between C and C++ [our software does not support Windows/MSVC], third place: differences in what casts are permitted/how they are done)

Re: Fun with C++26 reflection: Keyword Arguments

#43

Post by dingi »

flakes wrote: post #38
hyperhello wrote: post #36

Earlier quoted context omitted.

The syntax? Probably a little. It’s a typeless C. As for what you can use it for, it’s limited to browsers, practically, so not really comparable.

> it’s limited to browsers, practically That massively ignores node.js and all of the many popular backend frameworks built on it today. JS might not be everyone's cup of tea, but it is certainly not limited to browsers, practically.

Which uses JS made for a browser with some modifications.

Re: Fun with C++26 reflection: Keyword Arguments

#44

Post by weinzierl »

SideQuark wrote: post #8
anon-3988 wrote: post #5

I just don't understand why some people are so fascinated by this. Can you all admit that this is not at all practical? I swear C++ folks like it for the sake of it. No other engineer do this. Only antiques people or whatever. Can you imagine an engineer that is adamant on using his mystifying bespoke tool instead of just using a ruler. "But what if I have to measure it in the 4th dimension!?". I was expecting someth…

Reflection is such an insanely useful tool that pretty much all modern languages have it. As usual C++ is 20 years behind language design and brings terrible syntax. But it is tremendously useful. https://en.wikipedia.org/wiki/List_of_reflective_programming...

The article is about compile-time reflection, which is not nearly as useful as what the Wikipedia article you linked is about. It's only upside is that it is "zero cost" by some definitions of cost.

Runtime reflection on the other hand is useful but it also puts up obstacles not easy to overcome. For example it is one major reason we still have no decent ahead-of-time compilation in Java.

Re: Fun with C++26 reflection: Keyword Arguments

#45

Post by harry8 »

arjonagelhout wrote: post #24
sky2224 wrote: post #20

Earlier quoted context omitted.

Isn't the reason why so many other languages have reflection due to the fact that they essentially have the information there from the get-go? For example, C# and Java have their intermediate language that has a bunch of meta information attached to it already or the info can be added easily if need be. Is C++ not more raw in its compilation process from code to object files? I mean sure, I guess meta-data could be a…

When I started out programming in C#, I used reflection sometimes to circumvent the language’s design and restrictions. This resulted in brittle and hard to reason about code. Reflection should never be used to do this. So I do think you’re right that reflection can (and will) be abused by beginners if present as a language feature. With that said, I don’t know much about the internals of the C++ compiler, but having…

>I think the important thing is just being able to serialize and deserialize POD structs to and from some representation (e.g. json). For more advanced data, such as images or specific binary (file) formats, it’s easier to write custom writing / reading, encoding / decoding logic.

Why not just use a visitor? (Genuine question, not c++ snark).

Re: Fun with C++26 reflection: Keyword Arguments

#46

Post by friendzis »

flakes wrote: post #38
hyperhello wrote: post #36

Earlier quoted context omitted.

The syntax? Probably a little. It’s a typeless C. As for what you can use it for, it’s limited to browsers, practically, so not really comparable.

> it’s limited to browsers, practically That massively ignores node.js and all of the many popular backend frameworks built on it today. JS might not be everyone's cup of tea, but it is certainly not limited to browsers, practically.

We don't even write utilities in JVM languages, because spawning whole JVM is generally considered too expensive.

Yet there are people who will happily spawn whole web browser and even go as far as recommend doing so. All because they can't even write a left-pad function.

Re: Fun with C++26 reflection: Keyword Arguments

#47

Post by pjmlp »

anon-3988 wrote: post #5

I just don't understand why some people are so fascinated by this. Can you all admit that this is not at all practical? I swear C++ folks like it for the sake of it. No other engineer do this. Only antiques people or whatever. Can you imagine an engineer that is adamant on using his mystifying bespoke tool instead of just using a ruler. "But what if I have to measure it in the 4th dimension!?". I was expecting someth…

Apparently you have not been around many Lisp, Python, Ruby, Haskel, Scala,... folks.

This kind of geekyness is surely loved by many, not only C++.

Re: Fun with C++26 reflection: Keyword Arguments

#48

Post by flohofwoe »

weinzierl wrote: post #44
SideQuark wrote: post #8

Earlier quoted context omitted.

Reflection is such an insanely useful tool that pretty much all modern languages have it. As usual C++ is 20 years behind language design and brings terrible syntax. But it is tremendously useful. https://en.wikipedia.org/wiki/List_of_reflective_programming...

The article is about compile-time reflection, which is not nearly as useful as what the Wikipedia article you linked is about. It's only upside is that it is "zero cost" by some definitions of cost. Runtime reflection on the other hand is useful but it also puts up obstacles not easy to overcome. For example it is one major reason we still have no decent ahead-of-time compilation in Java.

I'm in the opposite camp, runtime reflection is useless, and almost always points to a design flaw while compile time reflection is actually useful (for obvious things like automatically building a serialization layer or an UI which represents the type, or building types from other types).

I'm sure that C++26 has implemented it in a way which is highly unpleasant to use though ;)

Re: Fun with C++26 reflection: Keyword Arguments

#50

Post by pjmlp »

weinzierl wrote: post #44
SideQuark wrote: post #8

Earlier quoted context omitted.

Reflection is such an insanely useful tool that pretty much all modern languages have it. As usual C++ is 20 years behind language design and brings terrible syntax. But it is tremendously useful. https://en.wikipedia.org/wiki/List_of_reflective_programming...

The article is about compile-time reflection, which is not nearly as useful as what the Wikipedia article you linked is about. It's only upside is that it is "zero cost" by some definitions of cost. Runtime reflection on the other hand is useful but it also puts up obstacles not easy to overcome. For example it is one major reason we still have no decent ahead-of-time compilation in Java.

We have add decent AOT compilation in Java almost since 2000, with Excelsior JET being one of the first vendors to offer it, but few are willing to pay for such tools.

Also I consider ART, GraalVM and OpenJ9 decent enough as free beer AOT.

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