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 #include <float.h>
22
nextafter(double x,double y)23 double nextafter(double x, double y)
24 {
25 int32_t hx,hy,ix,iy;
26 u_int32_t lx,ly;
27
28 EXTRACT_WORDS(hx,lx,x);
29 EXTRACT_WORDS(hy,ly,y);
30 ix = hx&0x7fffffff; /* |x| */
31 iy = hy&0x7fffffff; /* |y| */
32
33 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
34 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
35 return x+y;
36 if(x==y) return y; /* x=y, return y */
37 if((ix|lx)==0) { /* x == 0 */
38 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
39 y = x*x;
40 if(y==x) return y; else return x; /* raise underflow flag */
41 }
42 if(hx>=0) { /* x > 0 */
43 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
44 if(lx==0) hx -= 1;
45 lx -= 1;
46 } else { /* x < y, x += ulp */
47 lx += 1;
48 if(lx==0) hx += 1;
49 }
50 } else { /* x < 0 */
51 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
52 if(lx==0) hx -= 1;
53 lx -= 1;
54 } else { /* x > y, x += ulp */
55 lx += 1;
56 if(lx==0) hx += 1;
57 }
58 }
59 hy = hx&0x7ff00000;
60 if(hy>=0x7ff00000) return x+x; /* overflow */
61 if(hy<0x00100000) { /* underflow */
62 y = x*x;
63 if(y!=x) { /* raise underflow flag */
64 INSERT_WORDS(y,hx,lx);
65 return y;
66 }
67 }
68 INSERT_WORDS(x,hx,lx);
69 return x;
70 }
71 libm_hidden_def(nextafter)
72 #if LDBL_MANT_DIG == DBL_MANT_DIG
73 strong_alias_untyped(nextafter, nexttoward)
74 libm_hidden_def(nexttoward)
75 #else
76 double nexttoward(double x, long double y)
77 {
78 return nextafter(x, y);
79 }
80 libm_hidden_def(nexttoward)
81 #endif
82