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---
s_nextafter.c (1958B)
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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 #ifndef lint
14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_nextafter.c,v 1.9 2005/01/23 22:56:08 das 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 #include "math.h"
25 #include "math_private.h"
26
27 double
28 nextafter(double x, double y)
29 {
30 int32_t hx,hy,ix,iy;
31 u_int32_t lx,ly;
32
33 EXTRACT_WORDS(hx,lx,x);
34 EXTRACT_WORDS(hy,ly,y);
35 ix = hx&0x7fffffff; /* |x| */
36 iy = hy&0x7fffffff; /* |y| */
37
38 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
39 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
40 return x+y;
41 if(x==y) return y; /* x=y, return y */
42 if((ix|lx)==0) { /* x == 0 */
43 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
44 y = x*x;
45 if(y==x) return y; else return x; /* raise underflow flag */
46 }
47 if(hx>=0) { /* x > 0 */
48 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
49 if(lx==0) hx -= 1;
50 lx -= 1;
51 } else { /* x < y, x += ulp */
52 lx += 1;
53 if(lx==0) hx += 1;
54 }
55 } else { /* x < 0 */
56 if(hy>=0||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 }
64 hy = hx&0x7ff00000;
65 if(hy>=0x7ff00000) return x+x; /* overflow */
66 if(hy<0x00100000) { /* underflow */
67 y = x*x;
68 if(y!=x) { /* raise underflow flag */
69 INSERT_WORDS(y,hx,lx);
70 return y;
71 }
72 }
73 INSERT_WORDS(x,hx,lx);
74 return x;
75 }