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 <float.h>
20
21 #include "math.h"
22 #include "math_private.h"
23
24 double
nextafter(double x,double y)25 nextafter(double x, double y)
26 {
27 volatile double t;
28 int32_t hx,hy,ix,iy;
29 u_int32_t lx,ly;
30
31 EXTRACT_WORDS(hx,lx,x);
32 EXTRACT_WORDS(hy,ly,y);
33 ix = hx&0x7fffffff; /* |x| */
34 iy = hy&0x7fffffff; /* |y| */
35
36 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
37 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
38 return x+y;
39 if(x==y) return y; /* x=y, return y */
40 if((ix|lx)==0) { /* x == 0 */
41 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
42 t = x*x;
43 if(t==x) return t; else return x; /* raise underflow flag */
44 }
45 if(hx>=0) { /* x > 0 */
46 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
47 if(lx==0) hx -= 1;
48 lx -= 1;
49 } else { /* x < y, x += ulp */
50 lx += 1;
51 if(lx==0) hx += 1;
52 }
53 } else { /* x < 0 */
54 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
55 if(lx==0) hx -= 1;
56 lx -= 1;
57 } else { /* x > y, x += ulp */
58 lx += 1;
59 if(lx==0) hx += 1;
60 }
61 }
62 hy = hx&0x7ff00000;
63 if(hy>=0x7ff00000) return x+x; /* overflow */
64 if(hy<0x00100000) { /* underflow */
65 t = x*x;
66 if(t!=x) { /* raise underflow flag */
67 INSERT_WORDS(y,hx,lx);
68 return y;
69 }
70 }
71 INSERT_WORDS(x,hx,lx);
72 return x;
73 }
74
75 #if (LDBL_MANT_DIG == 53)
76 __weak_reference(nextafter, nexttoward);
77 __weak_reference(nextafter, nexttowardl);
78 __weak_reference(nextafter, nextafterl);
79 #endif
80