On 18/01/2025 17:56, Peter Dimov via Boost wrote:
John Maddock wrote:
Chris, Rubin, I *think* you are somewhat talking about different things here...
Rubin's point was that if you have a literal such as
1.2345678912345678_DD
Then the type computed is a decimal64 and the result will be rounded to 16 decimal places. This is true regardless of whether it is subsequently static_cast to something else (potentially causing double rounding).
So... I'm *reasonably* sure that Chris's argument doesn't hold so much water.
But, I do see one argument against a compile time assert, which is the "this is a right pain in the butt" argument, basically that users may not want to be forced to round all the arguments themselves, and/or that this may be error prone: have you counted exactly 16 digits and not accidentally rounded to 15? Plus string streaming will presumably round excess digits so it kind of makes sense to be consistent. A better option than failing here is probably to issue a warning, but constexpr_warn_str is still years away. Indeed, this would be perfect for that!
https://isocpp.org/files/papers/P2758R4.html
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