modf.c

操作系统SunOS 4.1.3版本的源码

#ifndef lint
static	char sccsid[] = "@(#)modf.c 1.1 92/07/30 SMI"; /* from ATT S5R3 */
#endif

/*	The following is extracted from...	*/

/*	Copyright (c) 1984 AT&T	*/
/*	  All Rights Reserved  	*/

/*	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T	*/
/*	The copyright notice above does not evidence any   	*/
/*	actual or intended publication of such source code.	*/

/*
 * modf(value, iptr) returns the signed fractional part of value
 * and stores the integer part indirectly through iptr.
 *
 */

#define MAXPOWTWO	4.503599627370496000E+15
			/* doubles >= MAXPOWTWO are already integers */
double
modf(value, iptr)
double value;
register double *iptr;
{
	register double absvalue;

	if ((absvalue = (value >= 0.0) ? value : -value) >= MAXPOWTWO)
		*iptr = value; /* it must be an integer */
	else {
		*iptr = absvalue + MAXPOWTWO; /* shift fraction off right */
		*iptr -= MAXPOWTWO; /* shift back without fraction */
		while (*iptr > absvalue) /* above arithmetic might round */
			*iptr -= 1.0; /* test again just to be sure */
		if (value < 0.0)
			*iptr = -*iptr;
	}
	return (value - *iptr); /* signed fractional part */
}