1*05a0b428SJohn Marino /* @(#)s_nextafter.c 5.1 93/09/24 */
2*05a0b428SJohn Marino /*
3*05a0b428SJohn Marino * ====================================================
4*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5*05a0b428SJohn Marino *
6*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
7*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
8*05a0b428SJohn Marino * software is freely granted, provided that this notice
9*05a0b428SJohn Marino * is preserved.
10*05a0b428SJohn Marino * ====================================================
11*05a0b428SJohn Marino */
12*05a0b428SJohn Marino
13*05a0b428SJohn Marino /* IEEE functions
14*05a0b428SJohn Marino * nextafter(x,y)
15*05a0b428SJohn Marino * return the next machine floating-point number of x in the
16*05a0b428SJohn Marino * direction toward y.
17*05a0b428SJohn Marino * Special cases:
18*05a0b428SJohn Marino */
19*05a0b428SJohn Marino
20*05a0b428SJohn Marino #include <float.h>
21*05a0b428SJohn Marino #include <math.h>
22*05a0b428SJohn Marino
23*05a0b428SJohn Marino #include "math_private.h"
24*05a0b428SJohn Marino
25*05a0b428SJohn Marino double
nextafter(double x,double y)26*05a0b428SJohn Marino nextafter(double x, double y)
27*05a0b428SJohn Marino {
28*05a0b428SJohn Marino int32_t hx,hy,ix,iy;
29*05a0b428SJohn Marino u_int32_t lx,ly;
30*05a0b428SJohn Marino
31*05a0b428SJohn Marino EXTRACT_WORDS(hx,lx,x);
32*05a0b428SJohn Marino EXTRACT_WORDS(hy,ly,y);
33*05a0b428SJohn Marino ix = hx&0x7fffffff; /* |x| */
34*05a0b428SJohn Marino iy = hy&0x7fffffff; /* |y| */
35*05a0b428SJohn Marino
36*05a0b428SJohn Marino if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
37*05a0b428SJohn Marino ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
38*05a0b428SJohn Marino return x+y;
39*05a0b428SJohn Marino if(x==y) return y; /* x=y, return y */
40*05a0b428SJohn Marino if((ix|lx)==0) { /* x == 0 */
41*05a0b428SJohn Marino INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
42*05a0b428SJohn Marino y = x*x;
43*05a0b428SJohn Marino if(y==x) return y; else return x; /* raise underflow flag */
44*05a0b428SJohn Marino }
45*05a0b428SJohn Marino if(hx>=0) { /* x > 0 */
46*05a0b428SJohn Marino if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
47*05a0b428SJohn Marino if(lx==0) hx -= 1;
48*05a0b428SJohn Marino lx -= 1;
49*05a0b428SJohn Marino } else { /* x < y, x += ulp */
50*05a0b428SJohn Marino lx += 1;
51*05a0b428SJohn Marino if(lx==0) hx += 1;
52*05a0b428SJohn Marino }
53*05a0b428SJohn Marino } else { /* x < 0 */
54*05a0b428SJohn Marino if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
55*05a0b428SJohn Marino if(lx==0) hx -= 1;
56*05a0b428SJohn Marino lx -= 1;
57*05a0b428SJohn Marino } else { /* x > y, x += ulp */
58*05a0b428SJohn Marino lx += 1;
59*05a0b428SJohn Marino if(lx==0) hx += 1;
60*05a0b428SJohn Marino }
61*05a0b428SJohn Marino }
62*05a0b428SJohn Marino hy = hx&0x7ff00000;
63*05a0b428SJohn Marino if(hy>=0x7ff00000) return x+x; /* overflow */
64*05a0b428SJohn Marino if(hy<0x00100000) { /* underflow */
65*05a0b428SJohn Marino y = x*x;
66*05a0b428SJohn Marino if(y!=x) { /* raise underflow flag */
67*05a0b428SJohn Marino INSERT_WORDS(y,hx,lx);
68*05a0b428SJohn Marino return y;
69*05a0b428SJohn Marino }
70*05a0b428SJohn Marino }
71*05a0b428SJohn Marino INSERT_WORDS(x,hx,lx);
72*05a0b428SJohn Marino return x;
73*05a0b428SJohn Marino }
74*05a0b428SJohn Marino
75*05a0b428SJohn Marino #if LDBL_MANT_DIG == DBL_MANT_DIG
76*05a0b428SJohn Marino __strong_alias(nextafterl, nextafter);
77*05a0b428SJohn Marino __strong_alias(nexttoward, nextafter);
78*05a0b428SJohn Marino __strong_alias(nexttowardl, nextafter);
79*05a0b428SJohn Marino #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
80