nextafter(3)

1NEXTAFTER(3)               Linux Programmer's Manual              NEXTAFTER(3)
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NAME

6       nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl
7       - floating-point number manipulation
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SYNOPSIS

10       #include <math.h>
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12       double nextafter(double x, double y);
13       float nextafterf(float x, float y);
14       long double nextafterl(long double x, long double y);
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16       double nexttoward(double x, long double y);
17       float nexttowardf(float x, long double y);
18       long double nexttowardl(long double x, long double y);
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20       Link with -lm.
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22   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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24       nextafter():
25           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
26               || _XOPEN_SOURCE >= 500
27               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
28               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
29       nextafterf(), nextafterl():
30           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
31               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
32               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
33       nexttoward(), nexttowardf(), nexttowardl():
34           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
35           _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

38       The  nextafter(),  nextafterf(),  and nextafterl() functions return the
39       next representable floating-point value following x in the direction of
40       y.  If y is less than x, these functions will return the largest repre‐
41       sentable number less than x.
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43       If x equals y, the functions return y.
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45       The nexttoward(), nexttowardf(), and  nexttowardl()  functions  do  the
46       same  as the corresponding nextafter() functions, except that they have
47       a long double second argument.
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RETURN VALUE

50       On success, these functions return  the  next  representable  floating-
51       point value after x in the direction of y.
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53       If x equals y, then y (cast to the same type as x) is returned.
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55       If x or y is a NaN, a NaN is returned.
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57       If  x  is  finite, and the result would overflow, a range error occurs,
58       and the functions return HUGE_VAL,  HUGE_VALF,  or  HUGE_VALL,  respec‐
59       tively, with the correct mathematical sign.
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61       If  x  is not equal to y, and the correct function result would be sub‐
62       normal, zero, or underflow, a range error occurs, and either  the  cor‐
63       rect value (if it can be represented), or 0.0, is returned.
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ERRORS

66       See  math_error(7) for information on how to determine whether an error
67       has occurred when calling these functions.
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69       The following errors can occur:
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71       Range error: result overflow
72              errno is set to ERANGE.  An  overflow  floating-point  exception
73              (FE_OVERFLOW) is raised.
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75       Range error: result is subnormal or underflows
76              errno  is  set to ERANGE.  An underflow floating-point exception
77              (FE_UNDERFLOW) is raised.
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ATTRIBUTES

80       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
81       tributes(7).
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83       ┌─────────────────────────────┬───────────────┬─────────┐
84       │Interface                    │ Attribute     │ Value   │
85       ├─────────────────────────────┼───────────────┼─────────┤
86       │nextafter(), nextafterf(),   │ Thread safety │ MT-Safe │
87       │nextafterl(), nexttoward(),  │               │         │
88       │nexttowardf(), nexttowardl() │               │         │
89       └─────────────────────────────┴───────────────┴─────────┘

CONFORMING TO

91       C99,  POSIX.1-2001,  POSIX.1-2008.  This function is defined in IEC 559
92       (and the appendix with recommended functions in IEEE 754/IEEE 854).
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BUGS

95       In glibc version 2.5 and earlier, these functions do not raise  an  un‐
96       derflow  floating-point  (FE_UNDERFLOW) exception when an underflow oc‐
97       curs.
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99       Before glibc version 2.23 these functions did not set errno.
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COLOPHON

105       This page is part of release 5.10 of the Linux  man-pages  project.   A
106       description  of  the project, information about reporting bugs, and the
107       latest    version    of    this    page,    can     be     found     at
108       https://www.kernel.org/doc/man-pages/.
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112GNU                               2020-12-21                      NEXTAFTER(3)