[vintermann]

I agree that's cool. It's usually sold as for finance applications, for compliance with rounding rules from the pre-binary era etc. But really, any number that lived as a decimal digit string somewhere in its lifetime should probably have been decimal throughout.

But I don't think it would have mattered here anyway. With finite precision floating point addition is not going to be associative, decimal or not.

[kstenerud]

In practice they don't need to be perfectly associative across all possible values, because most real-world calculations tend to stay within a few orders of magnitude, and don't require more than 10-15 significant digits (even for Earth orbital calculations). Once you need more than that, you'd have to use a multi-word numeric format regardless (same as if your operations started overflowing your largest int type).