Ultrix-3.1/src/libm/fmod.c

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/**********************************************************************
 *   Copyright (c) Digital Equipment Corporation 1984, 1985, 1986.    *
 *   All Rights Reserved. 					      *
 *   Reference "/usr/src/COPYRIGHT" for applicable restrictions.      *
 **********************************************************************/

/*	SCCSID: @(#)fmod.c	3.0	4/22/86	*/
/*	(System 5)  fmod.c	1.7	*/
/*LINTLIBRARY*/
/*
 *	fmod(x, y) returns the remainder of x on division by y,
 *	with the same sign as x,
 *	except that if |y| << |x|, it returns 0.
 */

#include <math.h>

double
fmod(x, y)
register double x, y;
{
	double d; /* can't be in register because of modf() below */

	/*
	 * The next lines determine if |y| is negligible compared to |x|,
	 * without dividing, and without adding values of the same sign.
	 */
	d = _ABS(x);
	if (d - _ABS(y) == d)
		return (0.0);
#ifndef	pdp11	/* pdp11 "cc" can't handle cast of double to void */
	(void)
#endif
	modf(x/y, &d); /* now it's safe to divide without overflow */
	return (x - d * y);
}