Ruby: missing/nextafter.c Source File

Ruby 3.3.6p108 (2024-11-05 revision 75015d4c1f6965b5e85e96fb309f1f2129f933c0)

nextafter.c
1#include "ruby/missing.h"
2
3#include <math.h>
4#include <float.h>
5
6/* This function doesn't set errno. It should on POSIX, though. */
7
8double
9nextafter(double x, double y)
10{
11 double x1, x2, d;
12 int e;
13
14 if (isnan(x))
15 return x;
16 if (isnan(y))
17 return y;
18
19 if (x == y)
20 return y;
21
22 if (x == 0) {
23 /* the minimum "subnormal" float */
24 x1 = ldexp(0.5, DBL_MIN_EXP - DBL_MANT_DIG + 1);
25 if (x1 == 0)
26 x1 = DBL_MIN; /* the minimum "normal" float */
27 if (0 < y)
28 return x1;
29 else
30 return -x1;
31 }
32
33 if (x < 0) {
34 if (isinf(x))
35 return -DBL_MAX;
36 if (x == -DBL_MAX && y < 0 && isinf(y))
37 return y;
38 }
39 else {
40 if (isinf(x))
41 return DBL_MAX;
42 if (x == DBL_MAX && 0 < y && isinf(y))
43 return y;
44 }
45
46 x1 = frexp(x, &e);
47
48 if (x < y) {
49 d = DBL_EPSILON/2;
50 if (x1 == -0.5) {
51 x1 *= 2;
52 e--;
53 }
54 }
55 else {
56 d = -DBL_EPSILON/2;
57 if (x1 == 0.5) {
58 x1 *= 2;
59 e--;
60 }
61 }
62
63 if (e < DBL_MIN_EXP) {
64 d = ldexp(d, DBL_MIN_EXP-e);
65 }
66
67 x2 = x1 + d;
68
69 if (x2 == 0.0) {
70 if (x1 < 0)
71 return -0.0;
72 else
73 return +0.0;
74 }
75
76 return ldexp(x2, e);
77}