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#if defined(LIBM_SCCS) && !defined(lint)
14static char rcsid[] = "$NetBSD: s_nextafter.c,v 1.8 1995/05/10 20:47:58 jtc Exp $";
15#endif
16
17/* IEEE functions
18 * nextafter(x,y)
19 * return the next machine floating-point number of x in the
20 * direction toward y.
21 * Special cases:
22 */
23
24/* Ugly hack so that the aliasing works. */
25#define __nexttoward __internal___nexttoward
26#define nexttoward __internal_nexttoward
27
28#include <errno.h>
29#include <math.h>
30#include <math-barriers.h>
31#include <math_private.h>
32#include <float.h>
33#include <libm-alias-double.h>
34
35double __nextafter(double x, double y)
36{
37 int32_t hx,hy,ix,iy;
38 uint32_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 double u;
51 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
52 u = math_opt_barrier (x);
53 u = u*u;
54 math_force_eval (u); /* raise underflow flag */
55 return x;
56 }
57 if(hx>=0) { /* x > 0 */
58 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
59 if(lx==0) hx -= 1;
60 lx -= 1;
61 } else { /* x < y, x += ulp */
62 lx += 1;
63 if(lx==0) hx += 1;
64 }
65 } else { /* x < 0 */
66 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
67 if(lx==0) hx -= 1;
68 lx -= 1;
69 } else { /* x > y, x += ulp */
70 lx += 1;
71 if(lx==0) hx += 1;
72 }
73 }
74 hy = hx&0x7ff00000;
75 if(hy>=0x7ff00000) {
76 double u = x+x; /* overflow */
77 math_force_eval (u);
78 __set_errno (ERANGE);
79 }
80 if(hy<0x00100000) {
81 double u = x*x; /* underflow */
82 math_force_eval (u); /* raise underflow flag */
83 __set_errno (ERANGE);
84 }
85 INSERT_WORDS(x,hx,lx);
86 return x;
87}
88libm_alias_double (__nextafter, nextafter)
89#ifdef NO_LONG_DOUBLE
90strong_alias (__nextafter, __nexttowardl)
91weak_alias (__nexttowardl, nexttowardl)
92#undef __nexttoward
93strong_alias (__nextafter, __nexttoward)
94#undef nexttoward
95weak_alias (__nextafter, nexttoward)
96#endif
97