On Monday, January 20th, 2025 at 11:52 AM, Klemens Morgenstern via Boost
On Wed, Jan 15, 2025 at 5:34 PM 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/
Boost.Decimal is an implementation of IEEE 754 https://standards.ieee.org/ieee/754/6210/ and ISO/IEC DTR 24733 https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2849.pdf Decimal Floating Point numbers. The library is header-only, has no dependencies, and requires C++14.
Thanks to Matt & Chris for submitting your library for review. From glancing at the docs it looks great. However, I got a very basic question:
What are the actual applications for decimal floating points? Where are they used or where would potential users want to use them?
The canonical example is finance. We have an example[1] where a user can parse a CSV of stock pricing data without the rounding error that would come with binary floating point, and then are able to perform analysis leveraging Boost.Math.
Why wouldn't one just use fixed-point arithmetic when the binary floating points don't provide the proper rounding behaviour?
In one of Reuben's questions he asked about emulating fixed-point and I believe that is possible, but have not tried to do it myself. We have a user who was using fixed-point arithmetic, but when they needed to support bitcoins it exceeded the precision of their fixed-point system so they either had to re-write or use an off the shelf solution like we offer here. They chose the latter and to my knowledge it has worked out for them. Matt [1] https://github.com/cppalliance/decimal/blob/develop/examples/statistics.cpp