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/* round.c
*
* Round double to nearest or even integer valued double
*
*
*
* SYNOPSIS:
*
* double x, y, round();
*
* y = round(x);
*
*
*
* DESCRIPTION:
*
* Returns the nearest integer to x as a double precision
* floating point result. If x ends in 0.5 exactly, the
* nearest even integer is chosen.
*
*
*
* ACCURACY:
*
* If x is greater than 1/(2*MACHEP), its closest machine
* representation is already an integer, so rounding does
* not change it.
*/
/*
Cephes Math Library Release 2.1: January, 1989
Copyright 1984, 1987, 1989 by Stephen L. Moshier
Direct inquiries to 30 Frost Street, Cambridge, MA 02140
*/
#include <math.h>
#ifdef ANSIPROT
double floor ( double );
#else
double floor();
#endif
double round(x)
double x;
{
double y, r;
/* Largest integer <= x */
y = floor(x);
/* Fractional part */
r = x - y;
/* Round up to nearest. */
if( r > 0.5 )
goto rndup;
/* Round to even */
if( r == 0.5 )
{
r = y - 2.0 * floor( 0.5 * y );
if( r == 1.0 )
{
rndup:
y += 1.0;
}
}
/* Else round down. */
return(y);
}
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