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 1.14 2014/03/18 18:20:37 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
__strong_alias(nextafterl,nextafter)29 __strong_alias(nextafterl, nextafter)
30 #endif
31
32 double
33 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 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
49 y = x*x;
50 if(y==x) return y; else return x; /* raise underflow flag */
51 }
52 if(hx>=0) { /* x > 0 */
53 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
54 if(lx==0) hx -= 1;
55 lx -= 1;
56 } else { /* x < y, x += ulp */
57 lx += 1;
58 if(lx==0) hx += 1;
59 }
60 } else { /* x < 0 */
61 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
62 if(lx==0) hx -= 1;
63 lx -= 1;
64 } else { /* x > y, x += ulp */
65 lx += 1;
66 if(lx==0) hx += 1;
67 }
68 }
69 hy = hx&0x7ff00000;
70 if(hy>=0x7ff00000) return x+x; /* overflow */
71 if(hy<0x00100000) { /* underflow */
72 y = x*x;
73 if(y!=x) { /* raise underflow flag */
74 INSERT_WORDS(y,hx,lx);
75 return y;
76 }
77 }
78 INSERT_WORDS(x,hx,lx);
79 return x;
80 }
81