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nextafter(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|ATTRIBUTES \|STANDARDS \|HISTORY \|BUGS \|SEE ALSO \|COLOPHON

nextafter(3)             Library Functions Manualnextafter(3)

NAME top

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

LIBRARY top

       Math library (libm,-lm)

SYNOPSIS top

#include <math.h>double nextafter(doublex, doubley);float nextafterf(floatx, floaty);long double nextafterl(long doublex, long doubley);double nexttoward(doublex, long doubley);float nexttowardf(floatx, long doubley);long double nexttowardl(long doublex, long doubley);   Feature Test Macro Requirements for glibc (seefeature_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_SOURCEnextafterf(),nextafterl():           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L               || /* Since glibc 2.19: */ _DEFAULT_SOURCE               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEnexttoward(),nexttowardf(),nexttowardl():           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE               || _POSIX_C_SOURCE >= 200112L

DESCRIPTION top

       Thenextafter(),nextafterf(), andnextafterl() functions return       the next representable floating-point value followingx in the       direction ofy.  Ify is less thanx, these functions will return       the largest representable number less thanx.       Ifx equalsy, the functions returny.       Thenexttoward(),nexttowardf(), andnexttowardl() functions do       the same as the correspondingnextafter() functions, except that       they have along double second argument.

RETURN VALUE top

       On success, these functions return the next representable       floating-point value afterx in the direction ofy.       Ifx equalsy, theny (cast to the same type asx) is returned.       Ifx ory is a NaN, a NaN is returned.       Ifx is finite, and the result would overflow, a range error       occurs, and the functions returnHUGE_VAL,HUGE_VALF, orHUGE_VALL, respectively, with the correct mathematical sign.       Ifx is not equal toy, 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.

ERRORS top

       Seemath_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 overflowerrno is set toERANGE.  An overflow floating-point              exception (FE_OVERFLOW) is raised.       Range error: result is subnormal or underflowserrno is set toERANGE.  An underflow floating-point              exception (FE_UNDERFLOW) is raised.

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │nextafter(),nextafterf(),           │ Thread safety │ MT-Safe │       │nextafterl(),nexttoward(),          │               │         │       │nexttowardf(),nexttowardl()         │               │         │       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

       C11, POSIX.1-2008.       This function is defined in IEC 559 (and the appendix with       recommended functions in IEEE 754/IEEE 854).

HISTORY top

       C99, POSIX.1-2001.

BUGS top

       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 seterrno.

COLOPHON top

       This page is part of theman-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 isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17nextafter(3)

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