Re: [RFC] decimal float point patch based on libdecnumber: testcase

Wu Zhou
2006-06-23T18:39:49Z

On Thu, 22 Jun 2006, Daniel Jacobowitz wrote:

> On Fri, Jun 23, 2006 at 07:27:29AM +0800, Wu Zhou wrote:
> > That is because they have different precision/exponent. Number
> > 1234567890123456.dd have 16 digits, its coefficient is 1234567890123456,
> > and exponent is 0, so it won't print back with an exponent. While in the
> > case of "1.2E10dd", the coefficient is 12, exponent is 9, so it will print
> > back with an exponent. And in exponent display mode, the coefficient will
> > be normalized, in this case, to 1.2; and exponent get to 10 respectively.
> >
> > For "p 1200000000000000.dd", it will return 1200000000000000. It is
> > equal to but different than 1.2E+15. Their precison is not the same.
>
> So they map down to different bit patterns. How bizarre.

Yes, they do. A little bizarre when I first saw this. But I don't feel
like this now. :-) It is desirable to be able to differentiate
between floating numbers with same value but different precision anyway.

>
> > Do you mean that we need to output something more close to the fact. to
> > say, "Addition/Multiple of decimal floating point is not supported right
> > now". or something other like this. If you want, I can do that.
>
> No, I think what's there is fine - but add a test or two for that error
> message.

OK. Understand. We can use XFAIL for them, right?

Regards
- Wu Zhou