C++23 added the ability to "print out" using formatting options a container directly instead of having to use some form of a loop to access each element individually. See:

https://github.com/Apress/beginning-cpp23/blob/main/Examples/Chapter%2005/Ex5_16.cpp

M'ok, the latest VS 2022 gets serious agita with this code, it only has partial support. :(

Luckily there is a workaround available:

https://github.com/Apress/beginning-cpp23/blob/main/Workarounds/format_ranges_workaround.h

#include that header after importing the stdlib and voila!


This is so mondo neato cool!

Something that shows up in later examples with this workaround are problems when declaring the container to be const. const std::vector v{ 1, 2, 3, 4 };

{fmt}, the 3rd party library that was used to create the C++ stdlib formatting features has zero problem dealing with a const container. I stare at the workaround code and honestly I can't figure out why it doesn't like const. std::formatter code overall I find opaque....

Something that shows up in later examples with this workaround are problems when declaring the container to be const

Try adding const on line 48, changing from this:
auto format(T& range, std::format_context& ctx) const
To this:
auto format(T const& range, std::format_context& ctx) const

I knew it would likely be something really simple that I was missing. Thank you very much, mbozzi!

FYI, I actually changed line 48 to
auto format(const T& range, std::format_context& ctx) const

Now the workaround works the same as the {fmt} library, const container or not.

Ah, the curse and bane of being a self-taught C++ hobbyist. *Sigh* So much I know I don't know.

Oh, I earlier commented out the first two lines in the workaround when I was originally getting the const issues. Well, that didn't work to correct the const problem. Obviously.


That way if you don't want to use the omnibus import std; it will work with importing individual C++ stdlib modules or including headers.

I think I will submit this const workaround change back to the authors' github.

Good to know and reminds me that I have more C++23 catching up to do.

I would recommend two books, one on C++20 and the other on C++23, by the same authors. The books have github repos, one I got the range formatting workaround from.

Beginning C++20: From Novice to Professional
https://link.springer.com/book/10.1007/978-1-4842-5884-2

Beginning C++23: From Beginner to Pro
https://link.springer.com/book/10.1007/978-1-4842-9343-0

Yes, they are eBooks, I have the C++20 book in a dead tree edition. And find it very flimsy and hard to read compared to the eBook.

I own both books and really recommend getting both. Each book cover much of the same material with examples and exercises of the other. The C++20 book has many of the examples/exercises that use modules in non-module form.

Visual Studio is still the only compiler that fully supports modules, even C++20 modules, though that is changing. No compiler is 100% compliant with C++23 yet.

I just recently did a re-read and code re-do of both books' code examples/exercises. Well worth the effort IMO 'cuz I learned some things I hadn't picked up on before.