1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12/* IEEE functions
13 *	nextafter(x,y)
14 *	return the next machine floating-point number of x in the
15 *	direction toward y.
16 *   Special cases:
17 */
18
19#include <float.h>
20
21#include "math.h"
22#include "math_private.h"
23
24double
25nextafter(double x, double y)
26{
27	volatile double t;
28	int32_t hx,hy,ix,iy;
29	u_int32_t lx,ly;
30
31	EXTRACT_WORDS(hx,lx,x);
32	EXTRACT_WORDS(hy,ly,y);
33	ix = hx&0x7fffffff;		/* |x| */
34	iy = hy&0x7fffffff;		/* |y| */
35
36	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
37	   ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
38	   return x+y;
39	if(x==y) return y;		/* x=y, return y */
40	if((ix|lx)==0) {			/* x == 0 */
41	    INSERT_WORDS(x,hy&0x80000000,1);	/* return +-minsubnormal */
42	    t = x*x;
43	    if(t==x) return t; else return x;	/* raise underflow flag */
44	}
45	if(hx>=0) {				/* x > 0 */
46	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */
47		if(lx==0) hx -= 1;
48		lx -= 1;
49	    } else {				/* x < y, x += ulp */
50		lx += 1;
51		if(lx==0) hx += 1;
52	    }
53	} else {				/* x < 0 */
54	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
55		if(lx==0) hx -= 1;
56		lx -= 1;
57	    } else {				/* x > y, x += ulp */
58		lx += 1;
59		if(lx==0) hx += 1;
60	    }
61	}
62	hy = hx&0x7ff00000;
63	if(hy>=0x7ff00000) return x+x;	/* overflow  */
64	if(hy<0x00100000) {		/* underflow */
65	    t = x*x;
66	    if(t!=x) {		/* raise underflow flag */
67	        INSERT_WORDS(y,hx,lx);
68		return y;
69	    }
70	}
71	INSERT_WORDS(x,hx,lx);
72	return x;
73}
74
75#if (LDBL_MANT_DIG == 53)
76__weak_reference(nextafter, nexttoward);
77__weak_reference(nextafter, nexttowardl);
78__weak_reference(nextafter, nextafterl);
79#endif
80