1/* @(#)s_nextafter.c 5.1 93/09/24 */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include <sys/cdefs.h>
14#if defined(LIBM_SCCS) && !defined(lint)
15__RCSID("$NetBSD: s_nextafter.c,v 1.17 2024/05/05 22:10:06 riastradh Exp $");
16#endif
17
18/* IEEE functions
19 *	nextafter(x,y)
20 *	return the next machine floating-point number of x in the
21 *	direction toward y.
22 *   Special cases:
23 */
24
25#include "math.h"
26#include "math_private.h"
27
28#ifndef __HAVE_LONG_DOUBLE
29__strong_alias(nextafterl, nextafter)
30__strong_alias(nexttoward, nextafter)
31__strong_alias(nexttowardl, nextafter)
32#endif
33
34double
35nextafter(double x, double y)
36{
37	int32_t hx,hy,ix,iy;
38	u_int32_t lx,ly;
39
40	EXTRACT_WORDS(hx,lx,x);
41	EXTRACT_WORDS(hy,ly,y);
42	ix = hx&0x7fffffff;		/* |x| */
43	iy = hy&0x7fffffff;		/* |y| */
44
45	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
46	   ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
47	   return x+y;
48	if(x==y) return y;		/* x=y, return y */
49	if((ix|lx)==0) {			/* x == 0 */
50	    INSERT_WORDS(x,hy&0x80000000,1);	/* return +-minsubnormal */
51	    y = x*x;
52	    if(y==x) return y; else return x;	/* raise underflow flag */
53	}
54	if(hx>=0) {				/* x > 0 */
55	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */
56		if(lx==0) hx -= 1;
57		lx -= 1;
58	    } else {				/* x < y, x += ulp */
59		lx += 1;
60		if(lx==0) hx += 1;
61	    }
62	} else {				/* x < 0 */
63	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
64		if(lx==0) hx -= 1;
65		lx -= 1;
66	    } else {				/* x > y, x += ulp */
67		lx += 1;
68		if(lx==0) hx += 1;
69	    }
70	}
71	hy = hx&0x7ff00000;
72	if(hy>=0x7ff00000) return x+x;	/* overflow  */
73	if(hy<0x00100000) {		/* underflow */
74	    y = x*x;
75	    if(y!=x) {		/* raise underflow flag */
76	        INSERT_WORDS(y,hx,lx);
77		return y;
78	    }
79	}
80	INSERT_WORDS(x,hx,lx);
81	return x;
82}
83