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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | BUGS | SEE ALSO | COLOPHON |
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nextafter(3) Library Functions Manual nextafter(3)
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf,
nexttowardl - floating-point number manipulation
Math library (libm, -lm)
#include <math.h>
double nextafter(double x, double y);
float nextafterf(float x, float y);
long double nextafterl(long double x, long double y);
double nexttoward(double x, long double y);
float nexttowardf(float x, long double y);
long double nexttowardl(long double x, long double y);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
nextafter():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
nextafterf(), nextafterl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
nexttoward(), nexttowardf(), nexttowardl():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
|| _POSIX_C_SOURCE >= 200112L
The nextafter(), nextafterf(), and nextafterl() functions return
the next representable floating-point value following x in the
direction of y. If y is less than x, these functions will return
the largest representable number less than x.
If x equals y, the functions return y.
The nexttoward(), nexttowardf(), and nexttowardl() functions do
the same as the corresponding nextafter() functions, except that
they have a long double second argument.
On success, these functions return the next representable
floating-point value after x in the direction of y.
If x equals y, then y (cast to the same type as x) is returned.
If x or y is a NaN, a NaN is returned.
If x is finite, and the result would overflow, a range error
occurs, and the functions return HUGE_VAL, HUGE_VALF, or
HUGE_VALL, respectively, with the correct mathematical sign.
If x is not equal to y, and the correct function result would be
subnormal, zero, or underflow, a range error occurs, and either
the correct value (if it can be represented), or 0.0, is returned.
See math_error(7) for information on how to determine whether an
error has occurred when calling these functions.
The following errors can occur:
Range error: result overflow
errno is set to ERANGE. An overflow floating-point
exception (FE_OVERFLOW) is raised.
Range error: result is subnormal or underflows
errno is set to ERANGE. An underflow floating-point
exception (FE_UNDERFLOW) is raised.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ nextafter(), nextafterf(), │ Thread safety │ MT-Safe │
│ nextafterl(), nexttoward(), │ │ │
│ nexttowardf(), nexttowardl() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
C99, POSIX.1-2001.
In glibc 2.5 and earlier, these functions do not raise an
underflow floating-point (FE_UNDERFLOW) exception when an
underflow occurs.
Before glibc 2.23 these functions did not set errno.
nearbyint(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 nextafter(3)
Pages that refer to this page: nextup(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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