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 /* IEEE functions
14 * nextafter(x,y)
15 * return the next machine floating-point number of x in the
16 * direction toward y.
17 * Special cases:
18 */
19
20 #include <float.h>
21 #include <math.h>
22
23 #include "math_private.h"
24
25 double
nextafter(double x,double y)26 nextafter(double x, double y)
27 {
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 y = x*x;
43 if(y==x) return y; 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 y = x*x;
66 if(y!=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 DEF_STD(nextafter);
75 LDBL_MAYBE_CLONE(nextafter);
76
77 #if LDBL_MANT_DIG == DBL_MANT_DIG
78 MAKE_UNUSED_CLONE(nexttoward, nextafter);
79 MAKE_UNUSED_CLONE(nexttowardl, nextafter);
80 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
81