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