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_private.h>
31#include <float.h>
32
33double __nextafter(double x, double y)
34{
35 int32_t hx,hy,ix,iy;
36 u_int32_t lx,ly;
37
38 EXTRACT_WORDS(hx,lx,x);
39 EXTRACT_WORDS(hy,ly,y);
40 ix = hx&0x7fffffff; /* |x| */
41 iy = hy&0x7fffffff; /* |y| */
42
43 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
44 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
45 return x+y;
46 if(x==y) return y; /* x=y, return y */
47 if((ix|lx)==0) { /* x == 0 */
48 double u;
49 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
50 u = math_opt_barrier (x);
51 u = u*u;
52 math_force_eval (u); /* raise underflow flag */
53 return x;
54 }
55 if(hx>=0) { /* x > 0 */
56 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
57 if(lx==0) hx -= 1;
58 lx -= 1;
59 } else { /* x < y, x += ulp */
60 lx += 1;
61 if(lx==0) hx += 1;
62 }
63 } else { /* x < 0 */
64 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
65 if(lx==0) hx -= 1;
66 lx -= 1;
67 } else { /* x > y, x += ulp */
68 lx += 1;
69 if(lx==0) hx += 1;
70 }
71 }
72 hy = hx&0x7ff00000;
73 if(hy>=0x7ff00000) {
74 double u = x+x; /* overflow */
75 math_force_eval (u);
76 __set_errno (ERANGE);
77 }
78 if(hy<0x00100000) {
79 double u = x*x; /* underflow */
80 math_force_eval (u); /* raise underflow flag */
81 __set_errno (ERANGE);
82 }
83 INSERT_WORDS(x,hx,lx);
84 return x;
85}
86weak_alias (__nextafter, nextafter)
87#ifdef NO_LONG_DOUBLE
88strong_alias (__nextafter, __nextafterl)
89weak_alias (__nextafter, nextafterl)
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