Date: Mon, 19 Jan 2004 14:13:14 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Bruce Evans <bde@zeta.org.au>, freebsd-standards@FreeBSD.ORG Subject: Re: Implementing C99's roundf(), round(), and roundl() Message-ID: <20040119221314.GA65652@troutmask.apl.washington.edu> In-Reply-To: <20040119213142.GA72803@VARK.homeunix.com> References: <20031129000133.GA30662@troutmask.apl.washington.edu> <20031129080911.GA25448@VARK.homeunix.com> <20031129163105.GA32651@troutmask.apl.washington.edu> <20031130213951.GA37082@VARK.homeunix.com> <20031201182219.O4431@gamplex.bde.org> <20031201203512.GA95524@troutmask.apl.washington.edu> <20031202091936.I8778@gamplex.bde.org> <20040119213142.GA72803@VARK.homeunix.com>
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On Mon, Jan 19, 2004 at 01:31:42PM -0800, David Schultz wrote:
>
> double
> round(double x)
> {
> double result;
> fp_except_t fe;
>
> fe = fpresetsticky(0);
> result = rint(x);
> if (fpgetsticky() & FP_X_IMP) {
> result = copysign(floor(fabs(x) + 0.5), x);
> fe |= FP_X_IMP;
> }
> fpresetsticky(fe);
> return (result);
> }
>
> Does this seem reasonable?
Don't you need
rnd = fpsetround(FP_RN); /* Set to known rounding mode */
result = rint(x);
fpsetround(rnd); /* Reset to whatever the user had */
to ensure that rint() rounds to an expected value.
int main(void) {
double u, v, x;
x = 0.5;
fpsetround(FP_RM);
u = round(x);
fpsetround(FP_RP);
v = round(x);
/* Does u equal v ? */
}
BTW, thanks for working on this issue.
--
Steve
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