ack/lang/cem/libcc.ansi/core/math/fmod.c

/* fmod function */
/* Author Robert R. Hall (hall@crach.cts.com) */

/* $Id$ */

#include <math.h>
#include <errno.h>

double(fmod)(double x, double y)
{ /* compute fmod(x, y) */
	double t;
	int n, neg;
	int ychar, xchar;

	if (y == 0.0)
	{
		errno = EDOM;
		return 0.0;
	}
	/* fmod(finite, finite) */
	if (y < 0.0)
		y = -y;
	if (x < 0.0)
		x = -x, neg = 1;
	else
		neg = 0;
	t = frexp(y, &ychar);
	/* substract |y| until |x| < |y| */

	t = frexp(x, &xchar);
	for (n = xchar - ychar; 0 <= n; --n)
	{
		/* try to substract |y|*2^n */
		t = ldexp(y, n);
		if (t <= x)
			x -= t;
	}
	return (neg ? -x : x);
}