On Monday, January 20th, 2025 at 2:29 PM, Fernando Pelliccioni via Boost
On Wed, Jan 15, 2025 at 10:34 AM John Maddock via Boost < boost@lists.boost.org> wrote:
The review of the proposed Decimal Number library by Matt Borland and Chris Kormanyos begins today and runs until 22nd Jan.
You will find documentation here: https://cppalliance.org/decimal/decimal.html
And the code repository is here: https://github.com/cppalliance/decimal/
Hi everyone,
First of all, a big thank you to Matt and Chris for your hard work, I personally find this library very useful. Here are a few quick comments:
1. Literals I agree with earlier suggestions about placing them in a separate namespace, such as boost::decimal::literals, rather than boost::decimal. This matches typical Boost conventions.
2. Headers I also concur with the feedback regarding compile times. Relying exclusively on
can be slow. Please provide smaller
headers.
There are issues open for 1 and 2 to be addressed.
3. Fast vs. Non-Fast Variants I think the authors’ choice of default is probably fine, though I’m not 100% certain. In any case, clearer documentation on when to pick the standard type vs. the fast variant would be really helpful. Some guidance on weighing storage vs. speed would benefit end users.
4. <cstdio> Support
I share the concerns about potentially unsafe functions and limited specifier support. Maybe focusing on <format> (for C++20) or a safer,
custom formatter would be more straightforward and less error-prone.
I think pushing people to charconv is the better move. <format> support needs GCC >= 13, Clang >= 18, or _MSC_VER >= 1940. That's a high bar for a C++14 library.
5. Concepts If the Concepts defined here are intended for user code, I agree they should be public and documented. I would like to use them in my C++20 (and beyond) code.
6. Hardware Decimal Support I don't see explicit mention of how this library could leverage hardware decimal capabilities, but I imagine that could be added in the future, possibly via a pull request from someone who has access to that hardware. It is a nice to have feature but not a must have. I would not stop the library from being released without it.
7. Compiler-Explorer support It would be great if this library was supported on Compiler-Explorer for doing some testing. I know it is not related to the library but it helps a lot for reviewing it.
8. Benchmarks I plan to run some additional benchmarks on my own machines. One thing I'm curious about is how the built-in GCC _Decimal32/_Decimal64 types compare. Do they behave more like the "standard" or the fast variants in practice?
"Standard", but I will note the behavior of the decimalXX, and decimalXX_fast are identical except the latter does not support sub-normals.
Thanks again! I think this library is shaping up wonderfully and can't wait to see how it evolves.
Best, Fernando
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost