Money type

[Ola Fosheim Grøstad]

On Thursday, 2 January 2020 at 18:26:25 UTC, Ola Fosheim Grøstad 
wrote:
> truncating.  E.g. you can do the same calculation twice with 
> round up/round down and do basic rounding. If you get the same 
> result, then it is right. But easy to make mistakes... like I 
> just demonstrated.. :-P

For those interested there work done on a standard for doing 
exactly this (interval arithmetics) called IEEE1788:

https://en.wikipedia.org/wiki/Interval_arithmetic#IEEE_Std_1788-2015_%E2%80%93_IEEE_standard_for_interval_arithmetic

So all computations are done twice, once rounding up and once 
rounding down. If the error gets too large then you can switch to 
a slower algorithm. So then you can safely do base 2 floating 
points using fast hardware without all the issues and fall back 
on a slower base 10 software implementation where it fails.