/* @(#)s_nextafter.c 1.3 95/01/18 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice 

 * is preserved.

 * ====================================================

 */

/* IEEE functions

 *	nextafter(x,y)

 *	return the next machine floating-point number of x in the

 *	direction toward y.

 *   Special cases:

 */

#include "fdlibm.h"

#ifdef __STDC__

	double nextafter(double x, double y)

#else

	double nextafter(x,y)

	double x,y;

#endif

{

	int	hx,hy,ix,iy;

	unsigned lx,ly;

	hx = __HI(x);		/* high word of x */

	lx = __LO(x);		/* low  word of x */

	hy = __HI(y);		/* high word of y */

	ly = __LO(y);		/* low  word of y */

	ix = hx&0x7fffffff;		/* |x| */

	iy = hy&0x7fffffff;		/* |y| */

	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */ 

	   ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */ 

	   return x+y;				

	if(x==y) return x;		/* x=y, return x */

	if((ix|lx)==0) {			/* x == 0 */

	    __HI(x) = hy&0x80000000;	/* return +-minsubnormal */

	    __LO(x) = 1;

	    y = x*x;

	    if(y==x) return y; else return x;	/* raise underflow flag */

	} 

	if(hx>=0) {				/* x > 0 */

	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */

		if(lx==0) hx -= 1;

		lx -= 1;

	    } else {				/* x < y, x += ulp */

		lx += 1;

		if(lx==0) hx += 1;

	    }

	} else {				/* x < 0 */

	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */

		if(lx==0) hx -= 1;

		lx -= 1;

	    } else {				/* x > y, x += ulp */

		lx += 1;

		if(lx==0) hx += 1;

	    }

	}

	hy = hx&0x7ff00000;

	if(hy>=0x7ff00000) return x+x;	/* overflow  */

	if(hy<0x00100000) {		/* underflow */

	    y = x*x;

	    if(y!=x) {		/* raise underflow flag */

		__HI(y) = hx; __LO(y) = lx;

		return y;

	    }

	}

	__HI(x) = hx; __LO(x) = lx;

	return x;

}