bigfloat II

[Paul D. Anderson]

Don Wrote:

> Paul D. Anderson wrote:
> > Does anyone have strong feelings for/against any of these options??
> > 
> > Paul
> 
> My opinion -- precision should be a per-object setting, since it is a 
> property of the data. Rounding etc is a property of the operators and 
> functions and should be thread-local, and set by creating a scope struct 
> with a constructor that sets the mode to a new value, and a destructor 
> which restores it to the previous one.
> 
> eg
>    BigFloat a = 5e50;
>    BigFloat b = 1e-20;
> {
>    BigFloatRounding(ROUND_DOWN); // applies until end of scope
>     a*=sin(b);
> }
> // we're back in round-to-nearest.
> 

I like that. I didn't consider scope as an option, but that's really what's wanted now that you've pointed it out.

I agree that precision is part of the data, but it needs to be considered as part of the operation as well. Multiplying two floats produces a number whose potential precision is the sum of the operands' precision. We need a method to determine what the precision of the product should be. Not that it's difficult to come up with an answer -- but we have to agree on something. That's what the context provides.

Thanks for your input.

Paul