Rev math

[curry]

>No, you must avoid operations that are inherently inaccurate. For
>instance, in the formula for the solutions of a quadratic equation
>only one of the plus/minus possibilities is guaranteed to be
>accurate. For a stable computation of the second you need to use a
>different formula completely.

Thanks to the explanations and try some more examples, I've got it 
now as far as the purposes I need it for. I'm thinking of using user 
input for operands of fairly simple calculations, so right now I 
won't need to worry too much about the kind of situations you 
mentioned such as using the result of one calculation for another and 
the cumulative loss in accuracy.

So for basic purposes, we can choose to limit or process user input 
or not for display purposes, but it will be just as accurate to use 
the raw number going into the calculation. Then we just round at an 
appropriate place. Sounds good to me.

Best wishes,

Curry