nextafterf(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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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30       nextafterf(), nextafterl():
31           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
32               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
33               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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35       nexttoward(), nexttowardf(), nexttowardl():
36           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
37               || _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

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

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

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

82       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
83       tributes(7).
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85       ┌────────────────────────────────────────────┬───────────────┬─────────┐
86       │Interface                                   │ Attribute     │ Value   │
87       ├────────────────────────────────────────────┼───────────────┼─────────┤
88       │nextafter(), nextafterf(), nextafterl(),    │ Thread safety │ MT-Safe │
89       │nexttoward(), nexttowardf(), nexttowardl()  │               │         │
90       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

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

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

107       This page is part of release 5.12 of the Linux  man-pages  project.   A
108       description  of  the project, information about reporting bugs, and the
109       latest    version    of    this    page,    can     be     found     at
110       https://www.kernel.org/doc/man-pages/.
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114GNU                               2021-03-22                      NEXTAFTER(3)