fast_float VS cppreference-doc

> Google put in significant engineering effort into "Ryu", a parsing library for double-precision floating point numbers: https://github.com/ulfjack/ryu

It's not a parsing library, but a printing one, i.e., double -> string. https://github.com/fastfloat/fast_float is a parsing library, i.e., string -> double, not by Google though, but was indeed motivated by parsing JSON fast https://lemire.me/blog/2020/03/10/fast-float-parsing-in-prac...

For those that don't know, gcc 12.x updated its float parsing logic to something similar to fast_float and it's about 1/6 of the cost presented here (sub 100 in the graph presented here). Strongly suggest using that library or upgrading the compiler if you need the performance.

This makes sense for integers but betware floating point from_chars - libc++ still doesn't implement it and libstdc++ implements it by wrapping locale-dependent libc functions which involves temporarily changing the thread locale and possibly memory allocation to make the passed string 0-terminated. IMO libstdc++'s checkbox "solution" is worse than not implementing it at all - user's are better off using Lemire's API-compatible fast_float implementation [0].

[0] https://github.com/fastfloat/fast_float

I'm a bit stuck on how to do the same thing in c++, due to containers only having a single type. The very inefficient way I'm currently doing it is by passing a program as a vector of strings, and then converting the string constants to doubles with the fast_float library.

Just above this comment is a merged PR, which references fast_float library: https://github.com/fastfloat/fast_float

Daniel Lemire @lemire (creator of the algorithm, author of the C++ implementation, and provided constant feedback to help guide the PR).

And out of 6,000 lines in the file, at least 3000 are other people's code: earcut for polygon triangulation and fast_float because .obj files typically contain a lot of floating point numbers so it's important to parse them quickly.

How this compares to https://github.com/fastfloat/fast_float ?

I tried to compare it against Daniel Lemire's excellent fast_float library. Fast float took about 180ms for the same program, and all I did was change "std" namespace prefix to "fast_float". It's a factor of 12 difference, at least my machine. I tried MSVC next, and it is a lot better, but it is still ~4 times slower than fast float. AFAIK, clang currently does not implement the feature at all.

If you don't mind a 3rd party lib until your stdlib updates, https://github.com/fastfloat/fast_float is best-in-class.

Rather than looking at good examples (which you should by all means do), add cppreference.com to you bookmarks and use it as your reference. By far the best C++ reference on the net. (from a C programmer who was thrown into C++ a decade ago -- slowly digesting C++20 now) Both StackOverflow.com and electronic.stackexchange.com are two additional QA sites that can help.

Sadly, not much. My method of learning is to get my hands dirty and waste a lot of time doing things wrong before I do them right. The only resource (outside of Google and StackOverflow) that I always had open was https://en.cppreference.com

In general, https://en.cppreference.com is your friend.

> As a C++ language reference I highly recommend https://en.cppreference.com

I'd be careful about such re-formulations of the Standard. When I was adding printf format checking to the D compiler, I discovered there were subtle discrepancies in the description of exactly how printf behaves. I went back to using the Standard.

Modern C++ code now looks very different to even C++11 code which is considered to be the start of modern C++.

"A Tour of C++" which has already been recommended is probably a good start to get back in the game. I think there was a new version coming out, but not sure what the current status about this is.

[https://en.cppreference.com](cppreference.com) is a good resource for me. It has documentation regarding the new standards as well and up to C++20 the examples are mostly complete, at least for the relevant things.

I can also recommend watching the "Back to Basics" talks on the CppCon youtube channel and once you are more familiar also the regular talks. They are great resources about practical topics.

Jason Turner's C++ Weekly videos are also a great resource. They are usually 10-15 minutes long videos that give you a good start to think about. Great way to learn something new every week.

At Google, at least, the style guide says to use snake case for variable names in C++ (but camel case for classes). As far as I can tell, this is also the convention in the C++ standard library.

Lets say that there's a file at https://en.cppreference.com/ called preferences.c. The command to download it would be wget https://en.cppreference.com/preferences.c

I would start with a direction of where to apply C++. Updating legacy code, working on embedded systems, creating financial application and creating high performant games are a few common option. Also sites like cppreference and Compiler Explorer/Godbolt are your friends in learning. CPlusPlus.com might help with legacy support as it stops with C++11.

Keep in mind that most YouTube C++ tutorials are garbage. Use www.learncpp.com instead as a tutorial, and https://en.cppreference.com as a language reference. Once you familiarize yourself with the language, you can learn the best practices using the C++ Core Guidelines.

The important thing to remember is that a concept exist and roughly what it's called, so you can look it up when you need to. You don't need to keep all the details in your head, that's what we have en.cppreference.com for.